Willow Grove NAS Weather Records (USW00014793)

Record envelope, standing records and threshold days for Willow Grove NAS (USW00014793), Pennsylvania, United States, with 67 years of record.

Key Facts for Willow Grove NAS

Willow Grove NAS (USW00014793) is a weather station in Pennsylvania, United States at 40.20 latitude and -75.15 longitude, 110 m (361 ft) above sea level.
The station reports from 1945 to 2011, 67 years of record.
1,464 records set at Willow Grove NAS still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Willow Grove NAS tied a daily record high maximum temperature of 26.1 C (79.0 F) on 18 March 2011.

About the Station

Location: Pennsylvania, United States, 40.20 latitude, -75.15 longitude.
Elevation: 110 m (361 ft).
Period of record: 1945 to 2011, 67 years.
Eligible elements: tmax, tmin, prcp, snow, snwd.

Daily Record Envelope and 2026

0 days at or beyond a record

The band shows the record high and record low for each calendar day at Willow Grove NAS. The lines show the 2026 daily maximum and minimum. 0 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.

Daily record high and record low at Willow Grove NAS, with 2026 drawn through them
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	22.8 C (73.0 F)	-22.8 C (-9.0 F)	n/a	n/a
Feb	23.9 C (75.0 F)	-21.1 C (-6.0 F)	n/a	n/a
Mar	31.1 C (88.0 F)	-15.0 C (5.0 F)	n/a	n/a
Apr	35.6 C (96.1 F)	-7.8 C (18.0 F)	n/a	n/a
May	36.1 C (97.0 F)	-1.7 C (28.9 F)	n/a	n/a
Jun	37.2 C (99.0 F)	3.9 C (39.0 F)	n/a	n/a
Jul	38.9 C (102.0 F)	9.4 C (48.9 F)	n/a	n/a
Aug	40.0 C (104.0 F)	6.1 C (43.0 F)	n/a	n/a
Sep	38.9 C (102.0 F)	1.1 C (34.0 F)	n/a	n/a
Oct	31.7 C (89.1 F)	-3.9 C (25.0 F)	n/a	n/a
Nov	28.3 C (82.9 F)	-10.6 C (12.9 F)	n/a	n/a
Dec	25.6 C (78.1 F)	-18.9 C (-2.0 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Willow Grove NAS still stand. 2002 holds the most, with 46.

Standing records at Willow Grove NAS by the year they were set
Year set	Standing records
1945	35
1946	29
1947	29
1948	17
1949	25
1950	25
1951	35
1952	19
1953	23
1954	23
1955	22
1956	25
1957	23
1958	17
1959	31
1960	23
1961	19
1962	20
1963	37
1964	25
1965	16
1966	20
1967	35
1968	19
1969	12
1970	28
1971	6
1972	22
1973	10
1974	14
1975	15
1976	28
1977	25
1978	22
1979	35
1980	16
1981	16
1982	24
1983	23
1984	29
1985	28
1986	20
1987	20
1988	30
1989	30
1990	31
1991	38
1992	13
1993	27
1994	11
1995	15
1996	25
1997	17
1998	17
1999	5
2000	23
2001	38
2002	46
2003	15
2004	8
2005	10
2006	14
2007	15
2008	14
2009	11
2010	23
2011	3

All-Time Record Progression

13 new records

13 all-time records were set at Willow Grove NAS between 17 January 1977 and 29 July 2002. Each dot is a new record.

When Willow Grove NAS set new all-time records
Date	Kind	Detail
1977-01-17	Record low maximum temperature	Record low maximum temperature -13.9 C (7.0 F)
1977-01-17	Record low minimum temperature	Record low minimum temperature -21.1 C (-6.0 F)
1982-01-17	Record low minimum temperature	Record low minimum temperature -22.8 C (-9.0 F)
1983-07-16	Record high minimum temperature	Record high minimum temperature 25.6 C (78.1 F)
1987-02-23	Record daily snowfall	Record daily snowfall 48.3 cm (19.0 in)
1988-08-13	Record high minimum temperature	Record high minimum temperature 26.7 C (80.1 F)
1996-01-07	Record daily snowfall	Record daily snowfall 55.9 cm (22.0 in)
1996-01-08	Record snow depth	Record snow depth 66.0 cm (26.0 in)
1996-01-09	Record snow depth	Record snow depth 68.6 cm (27.0 in)
1999-09-16	Record daily precipitation	Record daily precipitation 190.0 mm (7.5 in)
2001-06-16	Record daily precipitation	Record daily precipitation 218.4 mm (8.6 in)
2001-08-09	Record high maximum temperature	Record high maximum temperature 40.0 C (104.0 F)
2002-07-29	Record high minimum temperature	Record high minimum temperature 27.2 C (81.0 F)

Wettest Day of Each Month

Jun: 218.4 mm (8.6 in)

The wettest day on record for each calendar month at Willow Grove NAS. The most was 218.4 mm (8.6 in) on 16 June 2001.

Record daily precipitation for each month at Willow Grove NAS
Month	Record daily precipitation (mm)	Date
Jan	78.2 mm (3.1 in)	24 January 1979
Feb	48.3 mm (1.9 in)	13 February 1966
Mar	69.3 mm (2.7 in)	20 March 1958
Apr	75.4 mm (3.0 in)	2 April 2005
May	71.1 mm (2.8 in)	11 May 1981
Jun	218.4 mm (8.6 in)	16 June 2001
Jul	114.6 mm (4.5 in)	26 July 1989
Aug	116.3 mm (4.6 in)	17 August 1993
Sep	190.0 mm (7.5 in)	16 September 1999
Oct	132.8 mm (5.2 in)	25 October 1980
Nov	105.2 mm (4.1 in)	8 November 1972
Dec	91.2 mm (3.6 in)	11 December 1992

Period of Record Coverage

1945 to 2011

67 years of record at Willow Grove NAS, 1945 to 2011. 2 years have data for under 90 percent of days and are left out of rankings: 1945, 2011.

Days with data per year at Willow Grove NAS
Year	Days with data	Share of year	Complete
1945	322	88%	No
1946	354	97%	Yes
1947	332	91%	Yes
1948	363	99%	Yes
1949	362	99%	Yes
1950	364	100%	Yes
1951	364	100%	Yes
1952	366	100%	Yes
1953	365	100%	Yes
1954	365	100%	Yes
1955	365	100%	Yes
1956	366	100%	Yes
1957	365	100%	Yes
1958	365	100%	Yes
1959	365	100%	Yes
1960	366	100%	Yes
1961	365	100%	Yes
1962	365	100%	Yes
1963	365	100%	Yes
1964	366	100%	Yes
1965	365	100%	Yes
1966	365	100%	Yes
1967	365	100%	Yes
1968	366	100%	Yes
1969	365	100%	Yes
1970	365	100%	Yes
1971	365	100%	Yes
1972	366	100%	Yes
1973	365	100%	Yes
1974	365	100%	Yes
1975	365	100%	Yes
1976	366	100%	Yes
1977	365	100%	Yes
1978	365	100%	Yes
1979	365	100%	Yes
1980	366	100%	Yes
1981	365	100%	Yes
1982	365	100%	Yes
1983	365	100%	Yes
1984	366	100%	Yes
1985	365	100%	Yes
1986	365	100%	Yes
1987	365	100%	Yes
1988	366	100%	Yes
1989	365	100%	Yes
1990	365	100%	Yes
1991	365	100%	Yes
1992	366	100%	Yes
1993	365	100%	Yes
1994	365	100%	Yes
1995	365	100%	Yes
1996	366	100%	Yes
1997	365	100%	Yes
1998	357	98%	Yes
1999	350	96%	Yes
2000	347	95%	Yes
2001	350	96%	Yes
2002	351	96%	Yes
2003	347	95%	Yes
2004	346	95%	Yes
2005	351	96%	Yes
2006	352	96%	Yes
2007	365	100%	Yes
2008	334	91%	Yes
2009	363	99%	Yes
2010	360	99%	Yes
2011	100	27%	No

Latest Records

Latest records at Willow Grove NAS
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
18 March 2011	Willow Grove NAS, US	daily high max (Tie)	26.1 C (79.0 F)	tie	21 years	3 of 100 (Routine)
10 March 2011	Willow Grove NAS, US	daily rain	48.0 mm (1.9 in)	10.2 mm (0.4 in)	16 years	20 of 100 (Routine)
6 March 2011	Willow Grove NAS, US	daily rain	56.6 mm (2.2 in)	17.7 mm (0.7 in)	52 years	37 of 100 (Notable)
25 February 2011	Willow Grove NAS, US	daily rain	22.4 mm (0.9 in)	3.3 mm (0.13 in)	36 years	20 of 100 (Routine)
18 February 2011	Willow Grove NAS, US	daily high min	10.6 C (51.1 F)	3.4 C (6.1 F)	29 years	20 of 100 (Routine)
18 February 2011	Willow Grove NAS, US	daily high max	21.1 C (70.0 F)	1.7 C (3.1 F)	29 years	16 of 100 (Routine)
17 February 2011	Willow Grove NAS, US	daily high max	18.9 C (66.0 F)	0.6 C (1.1 F)	35 years	17 of 100 (Routine)
26 January 2011	Willow Grove NAS, US	daily snowfall	20.3 cm (8.0 in)	7.9 cm (3.1 in)	49 years	32 of 100 (Routine)
12 January 2011	Willow Grove NAS, US	daily snowfall	6.4 cm (2.5 in)	1.8 cm (0.7 in)	15 years	12 of 100 (Routine)
1 December 2010	Willow Grove NAS, US	daily rain	46.5 mm (1.8 in)	18.8 mm (0.7 in)	13 years	25 of 100 (Routine)
17 November 2010	Willow Grove NAS, US	daily high min	10.0 C (50.0 F)	1.1 C (2.0 F)	47 years	22 of 100 (Routine)
4 November 2010	Willow Grove NAS, US	daily rain	30.0 mm (1.2 in)	4.1 mm (0.16 in)	63 years	27 of 100 (Routine)
27 October 2010	Willow Grove NAS, US	daily high min (Tie)	17.2 C (63.0 F)	tie	25 years	3 of 100 (Routine)
4 October 2010	Willow Grove NAS, US	daily rain	13.0 mm (0.5 in)	2.1 mm (0.08 in)	9 years	9 of 100 (Routine)
1 October 2010	Willow Grove NAS, US	daily rain	68.8 mm (2.7 in)	36.5 mm (1.4 in)	52 years	46 of 100 (Notable)
30 September 2010	Willow Grove NAS, US	daily rain	72.1 mm (2.8 in)	14.7 mm (0.6 in)	31 years	23 of 100 (Routine)
28 September 2010	Willow Grove NAS, US	daily high min	20.0 C (68.0 F)	0.6 C (1.1 F)	64 years	26 of 100 (Routine)
22 September 2010	Willow Grove NAS, US	daily high max	33.3 C (91.9 F)	0.5 C (0.9 F)	40 years	19 of 100 (Routine)
12 September 2010	Willow Grove NAS, US	daily low max	17.8 C (64.0 F)	0.5 C (0.9 F)	44 years	20 of 100 (Routine)
24 July 2010	Willow Grove NAS, US	all-time high min (Tie)	27.2 C (81.0 F)	tie	7 years	7 of 100 (Routine)

Climate Trend

63 complete years, 1946 to 2010

One stripe for each of 63 complete years at Willow Grove NAS, 1946 to 2010. Blue stripes are years cooler than the station's own mean of 11.9 C (53.4 F); red stripes are warmer. The coolest year was 1978, at 10.2 C (50.3 F), and the warmest was 2001, at 14.3 C (57.8 F). The strongest colour marks a difference of 2.5 C (4.5 F).

Annual mean temperature at Willow Grove NAS as warming stripes, 1946 to 2010
Year	Annual mean temperature	Difference from the station mean
1946	12.4 C	+0.52 C
1948	11.3 C	-0.58 C
1949	12.9 C	+0.98 C
1950	11.0 C	-0.93 C
1951	11.6 C	-0.32 C
1952	12.0 C	+0.12 C
1953	12.6 C	+0.73 C
1954	11.7 C	-0.16 C
1955	11.6 C	-0.26 C
1956	11.3 C	-0.55 C
1957	12.0 C	+0.07 C
1958	10.5 C	-1.36 C
1959	12.2 C	+0.33 C
1960	11.3 C	-0.59 C
1961	11.6 C	-0.29 C
1962	10.7 C	-1.20 C
1963	10.9 C	-1.03 C
1964	11.2 C	-0.73 C
1965	11.0 C	-0.94 C
1966	11.0 C	-0.86 C
1967	10.5 C	-1.44 C
1968	11.1 C	-0.79 C
1969	11.1 C	-0.77 C
1970	11.0 C	-0.87 C
1971	12.0 C	+0.07 C
1972	10.7 C	-1.19 C
1973	12.3 C	+0.39 C
1974	12.1 C	+0.24 C
1975	12.1 C	+0.22 C
1976	11.3 C	-0.62 C
1977	11.2 C	-0.67 C
1978	10.2 C	-1.70 C
1979	11.3 C	-0.61 C
1980	11.2 C	-0.73 C
1981	11.1 C	-0.78 C
1982	11.2 C	-0.66 C
1983	12.4 C	+0.48 C
1984	12.3 C	+0.38 C
1985	12.7 C	+0.82 C
1986	12.7 C	+0.77 C
1987	12.9 C	+1.04 C
1988	12.4 C	+0.52 C
1989	12.3 C	+0.39 C
1990	13.8 C	+1.94 C
1991	13.4 C	+1.52 C
1992	11.8 C	-0.11 C
1993	12.5 C	+0.64 C
1994	12.3 C	+0.43 C
1995	11.2 C	-0.68 C
1996	11.5 C	-0.41 C
1997	11.3 C	-0.61 C
1998	13.1 C	+1.17 C
1999	12.5 C	+0.59 C
2000	12.6 C	+0.73 C
2001	14.3 C	+2.42 C
2002	14.1 C	+2.25 C
2003	11.3 C	-0.55 C
2004	12.0 C	+0.14 C
2005	12.3 C	+0.40 C
2006	13.1 C	+1.22 C
2007	12.5 C	+0.56 C
2009	11.7 C	-0.22 C
2010	13.0 C	+1.07 C

The annual mean temperature here has risen by 0.2 C (0.1 to 0.3) per decade over 1946 to 2010. In Fahrenheit: 0.4 F (0.2 to 0.6) per decade. The slope is a straight line fitted to 63 complete years; the brackets give its 95 percent interval.

Fitted temperature trends per decade at Willow Grove NAS
Measure	Per decade (C)	Per decade (F)	Period	Complete years	Reading
Annual mean temperature	0.2 C (0.1 to 0.3) per decade	0.4 F (0.2 to 0.6) per decade	1946 to 2010	63	Rise
Mean daily maximum	0.2 C (0.1 to 0.4) per decade	0.4 F (0.2 to 0.7) per decade	1946 to 2010	63	Rise
Mean daily minimum	0.2 C (0.1 to 0.3) per decade	0.4 F (0.2 to 0.5) per decade	1946 to 2010	63	Rise

A year is complete when all 12 months have at least 20 days of both daily maximum and daily minimum readings. The annual mean is the mean of the monthly means. The trend describes this one station over this period; it does not say what caused the change.

Extremes by Year

1945 to 2011

Yearly extremes at Willow Grove NAS: the record and the median year
Measure	Record	Year of the record	Median year	Years with a value
Hottest day (TXx)	40.0 C (104.0 F)	2001	35.6 C (96.1 F)	67
Coldest night (TNn)	-22.8 C (-9.0 F)	1982	-16.1 C (3.0 F)	67
Wettest day (Rx1day)	218.4 mm (8.6 in)	2001	71.1 mm (2.8 in)	67
Wettest five days (Rx5day)	259.8 mm (10.2 in)	2001	103.6 mm (4.1 in)	67
Longest dry spell (CDD)	36 days	2007	18 days	67

Hottest day (TXx)

The hottest day of the year at Willow Grove NAS, 1945 to 2011. The record is 40.0 C (104.0 F) in 2001, marked on the chart; the median year is 35.6 C (96.1 F).

Hottest day (TXx) at Willow Grove NAS by year
Year	Hottest day (TXx)
1945	35.6 C (96.1 F)
1946	35.6 C (96.1 F)
1947	33.9 C (93.0 F)
1948	36.7 C (98.1 F)
1949	36.1 C (97.0 F)
1950	33.9 C (93.0 F)
1951	35.6 C (96.1 F)
1952	37.2 C (99.0 F)
1953	38.9 C (102.0 F)
1954	37.8 C (100.0 F)
1955	37.2 C (99.0 F)
1956	35.6 C (96.1 F)
1957	38.9 C (102.0 F)
1958	34.4 C (93.9 F)
1959	36.1 C (97.0 F)
1960	33.3 C (91.9 F)
1961	35.0 C (95.0 F)
1962	35.0 C (95.0 F)
1963	36.7 C (98.1 F)
1964	35.6 C (96.1 F)
1965	33.9 C (93.0 F)
1966	38.9 C (102.0 F)
1967	33.3 C (91.9 F)
1968	33.9 C (93.0 F)
1969	33.9 C (93.0 F)
1970	33.3 C (91.9 F)
1971	35.6 C (96.1 F)
1972	33.3 C (91.9 F)
1973	35.0 C (95.0 F)
1974	33.9 C (93.0 F)
1975	35.0 C (95.0 F)
1976	33.9 C (93.0 F)
1977	36.1 C (97.0 F)
1978	33.9 C (93.0 F)
1979	33.3 C (91.9 F)
1980	38.3 C (100.9 F)
1981	35.0 C (95.0 F)
1982	32.8 C (91.0 F)
1983	35.6 C (96.1 F)
1984	36.7 C (98.1 F)
1985	35.6 C (96.1 F)
1986	37.2 C (99.0 F)
1987	36.7 C (98.1 F)
1988	38.9 C (102.0 F)
1989	35.6 C (96.1 F)
1990	36.1 C (97.0 F)
1991	37.8 C (100.0 F)
1992	35.6 C (96.1 F)
1993	37.8 C (100.0 F)
1994	36.7 C (98.1 F)
1995	37.8 C (100.0 F)
1996	36.1 C (97.0 F)
1997	35.6 C (96.1 F)
1998	32.8 C (91.0 F)
1999	36.1 C (97.0 F)
2000	35.0 C (95.0 F)
2001	40.0 C (104.0 F)
2002	38.9 C (102.0 F)
2003	32.8 C (91.0 F)
2004	32.8 C (91.0 F)
2005	35.0 C (95.0 F)
2006	35.6 C (96.1 F)
2007	35.0 C (95.0 F)
2008	35.0 C (95.0 F)
2009	33.3 C (91.9 F)
2010	38.3 C (100.9 F)
2011	26.1 C (79.0 F)

Coldest night (TNn)

The coldest night of the year at Willow Grove NAS, 1945 to 2011. The record is -22.8 C (-9.0 F) in 1982, marked on the chart; the median year is -16.1 C (3.0 F).

Coldest night (TNn) at Willow Grove NAS by year
Year	Coldest night (TNn)
1945	-12.8 C (9.0 F)
1946	-14.4 C (6.1 F)
1947	-16.1 C (3.0 F)
1948	-19.4 C (-2.9 F)
1949	-11.7 C (10.9 F)
1950	-16.1 C (3.0 F)
1951	-18.3 C (-0.9 F)
1952	-15.0 C (5.0 F)
1953	-11.7 C (10.9 F)
1954	-17.2 C (1.0 F)
1955	-17.2 C (1.0 F)
1956	-12.2 C (10.0 F)
1957	-17.2 C (1.0 F)
1958	-15.6 C (3.9 F)
1959	-14.4 C (6.1 F)
1960	-15.0 C (5.0 F)
1961	-20.0 C (-4.0 F)
1962	-18.3 C (-0.9 F)
1963	-17.8 C (0.0 F)
1964	-16.1 C (3.0 F)
1965	-17.8 C (0.0 F)
1966	-15.0 C (5.0 F)
1967	-18.3 C (-0.9 F)
1968	-18.3 C (-0.9 F)
1969	-12.8 C (9.0 F)
1970	-17.8 C (0.0 F)
1971	-16.1 C (3.0 F)
1972	-16.1 C (3.0 F)
1973	-15.6 C (3.9 F)
1974	-11.1 C (12.0 F)
1975	-11.1 C (12.0 F)
1976	-15.6 C (3.9 F)
1977	-21.1 C (-6.0 F)
1978	-16.7 C (1.9 F)
1979	-21.1 C (-6.0 F)
1980	-18.9 C (-2.0 F)
1981	-21.1 C (-6.0 F)
1982	-22.8 C (-9.0 F)
1983	-17.2 C (1.0 F)
1984	-20.6 C (-5.1 F)
1985	-21.1 C (-6.0 F)
1986	-13.3 C (8.1 F)
1987	-17.8 C (0.0 F)
1988	-17.8 C (0.0 F)
1989	-14.4 C (6.1 F)
1990	-12.2 C (10.0 F)
1991	-13.9 C (7.0 F)
1992	-12.2 C (10.0 F)
1993	-16.7 C (1.9 F)
1994	-18.9 C (-2.0 F)
1995	-16.7 C (1.9 F)
1996	-16.7 C (1.9 F)
1997	-15.0 C (5.0 F)
1998	-11.1 C (12.0 F)
1999	-12.8 C (9.0 F)
2000	-15.0 C (5.0 F)
2001	-11.7 C (10.9 F)
2002	-10.0 C (14.0 F)
2003	-17.2 C (1.0 F)
2004	-16.1 C (3.0 F)
2005	-16.1 C (3.0 F)
2006	-10.6 C (12.9 F)
2007	-13.9 C (7.0 F)
2008	-13.2 C (8.2 F)
2009	-18.2 C (-0.8 F)
2010	-12.7 C (9.1 F)
2011	-16.6 C (2.1 F)

Wettest day (Rx1day)

The wettest day of the year at Willow Grove NAS, 1945 to 2011. The record is 218.4 mm (8.6 in) in 2001, marked on the chart; the median year is 71.1 mm (2.8 in).

Wettest day (Rx1day) at Willow Grove NAS by year
Year	Wettest day (Rx1day)
1945	70.6 mm (2.8 in)
1946	86.4 mm (3.4 in)
1947	61.0 mm (2.4 in)
1948	45.5 mm (1.8 in)
1949	38.1 mm (1.5 in)
1950	105.7 mm (4.2 in)
1951	59.7 mm (2.4 in)
1952	65.5 mm (2.6 in)
1953	57.2 mm (2.3 in)
1954	67.3 mm (2.6 in)
1955	93.7 mm (3.7 in)
1956	44.5 mm (1.8 in)
1957	36.3 mm (1.4 in)
1958	69.3 mm (2.7 in)
1959	79.8 mm (3.1 in)
1960	122.7 mm (4.8 in)
1961	64.5 mm (2.5 in)
1962	47.8 mm (1.9 in)
1963	49.0 mm (1.9 in)
1964	73.4 mm (2.9 in)
1965	65.8 mm (2.6 in)
1966	87.4 mm (3.4 in)
1967	53.3 mm (2.1 in)
1968	75.4 mm (3.0 in)
1969	85.3 mm (3.4 in)
1970	64.5 mm (2.5 in)
1971	72.9 mm (2.9 in)
1972	105.2 mm (4.1 in)
1973	143.5 mm (5.6 in)
1974	62.7 mm (2.5 in)
1975	94.2 mm (3.7 in)
1976	37.8 mm (1.5 in)
1977	79.0 mm (3.1 in)
1978	84.3 mm (3.3 in)
1979	78.2 mm (3.1 in)
1980	132.8 mm (5.2 in)
1981	71.1 mm (2.8 in)
1982	64.0 mm (2.5 in)
1983	61.7 mm (2.4 in)
1984	54.6 mm (2.1 in)
1985	79.2 mm (3.1 in)
1986	65.3 mm (2.6 in)
1987	48.3 mm (1.9 in)
1988	72.6 mm (2.9 in)
1989	114.6 mm (4.5 in)
1990	108.5 mm (4.3 in)
1991	72.1 mm (2.8 in)
1992	91.2 mm (3.6 in)
1993	116.3 mm (4.6 in)
1994	83.3 mm (3.3 in)
1995	68.6 mm (2.7 in)
1996	98.6 mm (3.9 in)
1997	59.9 mm (2.4 in)
1998	48.8 mm (1.9 in)
1999	190.0 mm (7.5 in)
2000	91.4 mm (3.6 in)
2001	218.4 mm (8.6 in)
2002	53.1 mm (2.1 in)
2003	52.3 mm (2.1 in)
2004	107.7 mm (4.2 in)
2005	96.0 mm (3.8 in)
2006	58.9 mm (2.3 in)
2007	6.4 mm (0.25 in)
2008	0.0 mm (0.00 in)
2009	103.9 mm (4.1 in)
2010	72.1 mm (2.8 in)
2011	56.6 mm (2.2 in)

Wettest five days (Rx5day)

The wettest five days of the year at Willow Grove NAS, 1945 to 2011. The record is 259.8 mm (10.2 in) in 2001, marked on the chart; the median year is 103.6 mm (4.1 in).

Wettest five days (Rx5day) at Willow Grove NAS by year
Year	Wettest five days (Rx5day)
1945	143.5 mm (5.6 in)
1946	124.8 mm (4.9 in)
1947	101.7 mm (4.0 in)
1948	83.6 mm (3.3 in)
1949	68.9 mm (2.7 in)
1950	108.0 mm (4.3 in)
1951	81.3 mm (3.2 in)
1952	116.5 mm (4.6 in)
1953	96.7 mm (3.8 in)
1954	82.3 mm (3.2 in)
1955	155.2 mm (6.1 in)
1956	92.1 mm (3.6 in)
1957	80.3 mm (3.2 in)
1958	103.6 mm (4.1 in)
1959	138.5 mm (5.5 in)
1960	163.1 mm (6.4 in)
1961	99.3 mm (3.9 in)
1962	93.6 mm (3.7 in)
1963	100.0 mm (3.9 in)
1964	82.8 mm (3.3 in)
1965	70.4 mm (2.8 in)
1966	94.8 mm (3.7 in)
1967	102.6 mm (4.0 in)
1968	96.2 mm (3.8 in)
1969	114.7 mm (4.5 in)
1970	81.1 mm (3.2 in)
1971	124.7 mm (4.9 in)
1972	120.9 mm (4.8 in)
1973	152.9 mm (6.0 in)
1974	71.0 mm (2.8 in)
1975	127.2 mm (5.0 in)
1976	67.1 mm (2.6 in)
1977	97.1 mm (3.8 in)
1978	101.9 mm (4.0 in)
1979	162.8 mm (6.4 in)
1980	134.8 mm (5.3 in)
1981	100.3 mm (3.9 in)
1982	80.2 mm (3.2 in)
1983	90.6 mm (3.6 in)
1984	147.4 mm (5.8 in)
1985	145.0 mm (5.7 in)
1986	118.1 mm (4.6 in)
1987	71.1 mm (2.8 in)
1988	122.6 mm (4.8 in)
1989	158.4 mm (6.2 in)
1990	135.4 mm (5.3 in)
1991	74.9 mm (2.9 in)
1992	123.2 mm (4.9 in)
1993	151.6 mm (6.0 in)
1994	115.7 mm (4.6 in)
1995	71.8 mm (2.8 in)
1996	107.6 mm (4.2 in)
1997	95.5 mm (3.8 in)
1998	115.0 mm (4.5 in)
1999	205.3 mm (8.1 in)
2000	116.5 mm (4.6 in)
2001	259.8 mm (10.2 in)
2002	57.7 mm (2.3 in)
2003	91.1 mm (3.6 in)
2004	112.6 mm (4.4 in)
2005	116.0 mm (4.6 in)
2006	58.9 mm (2.3 in)
2007	6.4 mm (0.25 in)
2008	0.0 mm (0.00 in)
2009	128.8 mm (5.1 in)
2010	155.2 mm (6.1 in)
2011	106.1 mm (4.2 in)

Longest dry spell (CDD)

The longest dry spell of the year at Willow Grove NAS, 1945 to 2011. The record is 36 days in 2007, marked on the chart; the median year is 18 days.

Longest dry spell (CDD) at Willow Grove NAS by year
Year	Longest dry spell (CDD)
1945	13 days
1946	33 days
1947	32 days
1948	19 days
1949	17 days
1950	15 days
1951	12 days
1952	16 days
1953	21 days
1954	17 days
1955	13 days
1956	13 days
1957	15 days
1958	20 days
1959	25 days
1960	12 days
1961	18 days
1962	14 days
1963	28 days
1964	18 days
1965	16 days
1966	18 days
1967	19 days
1968	26 days
1969	16 days
1970	16 days
1971	20 days
1972	14 days
1973	26 days
1974	13 days
1975	12 days
1976	23 days
1977	18 days
1978	18 days
1979	10 days
1980	24 days
1981	15 days
1982	21 days
1983	18 days
1984	12 days
1985	18 days
1986	19 days
1987	16 days
1988	22 days
1989	15 days
1990	13 days
1991	23 days
1992	12 days
1993	12 days
1994	18 days
1995	20 days
1996	8 days
1997	14 days
1998	29 days
1999	20 days
2000	21 days
2001	20 days
2002	14 days
2003	15 days
2004	18 days
2005	27 days
2006	29 days
2007	36 days
2008	23 days
2009	15 days
2010	19 days
2011	16 days

Each chart shows one value per year; the dot marks the record year. TXx is the hottest daily maximum, TNn the coldest daily minimum, Rx1day and Rx5day the largest one-day and five-day rain totals, and CDD the longest run of days with less than 1 mm of rain. A year with missing days can understate an extreme.

Frost Dates and Growing Season

63 years with a frost

Across 63 years with a frost, the median last spring frost at Willow Grove NAS falls on 12 April and the median first autumn frost on 27 October, which leaves a median of 200 days between them.

In 1980 to 2010 the median growing season was 202 days. That is 3 days more than in 1946 to 1976.

Fitted over all years, the growing season changes by +1.6 days per decade at this station.

Frost dates and growing season at Willow Grove NAS
Measure	Median, all years	Earliest period (1946 to 1976)	Recent period (1980 to 2010)	Recent against earliest	Fitted trend
Last spring frost	12 April	12 April	11 April	1 day earlier	-0.8 days per decade
First autumn frost	27 October	28 October	29 October	1 day later	+0.8 days per decade
Growing days	200 days	199 days	202 days	3 days more	+1.6 days per decade

A frost day is a day with a daily minimum at or below 0 C (32 F). The last spring frost and the first autumn frost are the last and first such days of the cold season, and growing days are the days between them. A negative trend for the last spring frost means it comes earlier.

Rainfall Return Levels

62 years, 1946 to 2010

A day with at least 71.4 mm (2.8 in) of rain is expected about once in 2 years. A day with at least 200.7 mm (7.9 in) of rain is expected about once in 100 years.

Rainfall return levels at Willow Grove NAS: the daily rain expected about once in a given number of years
Expected about once in	A day with at least	Note
2 years	71.4 mm (2.8 in)
5 years	98.0 mm (3.9 in)
10 years	118.5 mm (4.7 in)
25 years	148.0 mm (5.8 in)
50 years	173.0 mm (6.8 in)
100 years	200.7 mm (7.9 in)	Longer than the 62 years of record

The levels come from a generalised extreme value (GEV) distribution fitted by L-moments to the wettest-day total of each year, 62 years of values from 1946 to 2010.

A return level is an estimate. It is least reliable for the long periods, 50 and 100 years, and for any period longer than the record behind the fit, where the fit has to reach past the largest day actually observed. It is not a forecast.

The largest wettest-day totals in the fit: 218.4 mm (8.6 in) in 2001; 190.0 mm (7.5 in) in 1999; 143.5 mm (5.6 in) in 1973.

Station Changes

No change in the annual mean temperature of this station was found against its neighbours.

Download the Data

Data for Willow Grove NAS standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Willow Grove NAS threshold days by year: CSV or JSON. Field meanings are on the data page.

Source: NOAA National Centers for Environmental Information, Global Historical Climatology Network Daily (GHCN-Daily). Records are computed by World Extreme Weather Monitor and are not official NOAA products. (US Government open data (NOAA NCEI)) Data as of 2026-10-15 (15 October 2026). Records are computed by this site and are not official.

Data as of 2025-12-31. Last revised 31 December 2025 (2025-12-31).