Natrona Lock 4 Weather Records (USC00366151)

Record envelope, standing records and threshold days for Natrona Lock 4 (USC00366151), Pennsylvania, United States, with 100 years of record.

Key Facts for Natrona Lock 4

Natrona Lock 4 (USC00366151) is a weather station in Pennsylvania, United States at 40.61 latitude and -79.72 longitude, 232 m (760 ft) above sea level.
The station reports from 1927 to 2026, 100 years of record.
1,464 records set at Natrona Lock 4 still stand.
Records are tracked for prcp, snow, snwd: an element needs 30 years of data to be eligible.
Natrona Lock 4 set a daily record precipitation of 26.9 mm (1.1 in) on 11 October 2026 (provisional).

Provisional Records

Records set in the last 60 days are provisional until they clear the revision window.

About the Station

Location: Pennsylvania, United States, 40.61 latitude, -79.72 longitude.
Elevation: 232 m (760 ft).
Period of record: 1927 to 2026, 100 years.
Eligible elements: prcp, snow, snwd.

Daily Record Envelope and 2026

52 days at or beyond a record

The band shows the record high and record low for each calendar day at Natrona Lock 4. The lines show the 2026 daily maximum and minimum. 52 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.

Daily record high and record low at Natrona Lock 4, with 2026 drawn through them
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	23.9 C (75.0 F)	-24.4 C (-11.9 F)	16.7 C (62.1 F)	-24.4 C (-11.9 F)
Feb	25.6 C (78.1 F)	-24.4 C (-11.9 F)	15.6 C (60.1 F)	-24.4 C (-11.9 F)
Mar	26.7 C (80.1 F)	-20.0 C (-4.0 F)	26.7 C (80.1 F)	-9.4 C (15.1 F)
Apr	30.0 C (86.0 F)	-6.7 C (19.9 F)	27.8 C (82.0 F)	-2.2 C (28.0 F)
May	34.4 C (93.9 F)	-1.1 C (30.0 F)	31.1 C (88.0 F)	1.7 C (35.1 F)
Jun	36.7 C (98.1 F)	3.3 C (37.9 F)	31.1 C (88.0 F)	6.1 C (43.0 F)
Jul	40.0 C (104.0 F)	9.4 C (48.9 F)	35.6 C (96.1 F)	9.4 C (48.9 F)
Aug	36.7 C (98.1 F)	7.2 C (45.0 F)	30.6 C (87.1 F)	11.1 C (52.0 F)
Sep	35.0 C (95.0 F)	3.9 C (39.0 F)	33.3 C (91.9 F)	5.6 C (42.1 F)
Oct	32.8 C (91.0 F)	-1.7 C (28.9 F)	24.4 C (75.9 F)	3.3 C (37.9 F)
Nov	26.7 C (80.1 F)	-9.4 C (15.1 F)	n/a	n/a
Dec	20.0 C (68.0 F)	-17.2 C (1.0 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Natrona Lock 4 still stand. 2017 holds the most, with 110.

Standing records at Natrona Lock 4 by the year they were set
Year set	Standing records
1977	25
1978	12
2011	87
2012	93
2013	100
2014	104
2015	109
2016	101
2017	110
2018	100
2019	67
2020	81
2021	85
2022	78
2023	84
2024	92
2025	67
2026	69

All-Time Record Progression

2 new records

2 all-time records were set at Natrona Lock 4 between 9 July 1985 and 18 September 2004. Each dot is a new record.

When Natrona Lock 4 set new all-time records
Date	Kind	Detail
1985-07-09	Record daily precipitation	Record daily precipitation 116.6 mm (4.6 in)
2004-09-18	Record daily precipitation	Record daily precipitation 144.8 mm (5.7 in)

Wettest Day of Each Month

Sep: 144.8 mm (5.7 in)

The wettest day on record for each calendar month at Natrona Lock 4. The most was 144.8 mm (5.7 in) on 18 September 2004.

Record daily precipitation for each month at Natrona Lock 4
Month	Record daily precipitation (mm)	Date
Jan	57.2 mm (2.3 in)	27 January 1952
Feb	51.1 mm (2.0 in)	16 February 2018
Mar	48.0 mm (1.9 in)	30 March 1928
Apr	66.8 mm (2.6 in)	12 April 1948
May	78.2 mm (3.1 in)	27 May 1987
Jun	86.4 mm (3.4 in)	15 June 2015
Jul	116.6 mm (4.6 in)	9 July 1985
Aug	86.4 mm (3.4 in)	31 August 1981
Sep	144.8 mm (5.7 in)	18 September 2004
Oct	108.2 mm (4.3 in)	16 October 1954
Nov	53.3 mm (2.1 in)	20 November 2003
Dec	78.5 mm (3.1 in)	1 December 2010

Period of Record Coverage

1977 to 2026

18 years of record at Natrona Lock 4, 1977 to 2026. 4 years have data for under 90 percent of days and are left out of rankings: 1977, 1978, 2012, 2026.

Days with data per year at Natrona Lock 4
Year	Days with data	Share of year	Complete
1977	25	7%	No
1978	30	8%	No
2011	356	98%	Yes
2012	316	86%	No
2013	359	98%	Yes
2014	359	98%	Yes
2015	359	98%	Yes
2016	366	100%	Yes
2017	365	100%	Yes
2018	360	99%	Yes
2019	359	98%	Yes
2020	363	99%	Yes
2021	359	98%	Yes
2022	352	96%	Yes
2023	360	99%	Yes
2024	352	96%	Yes
2025	336	92%	Yes
2026	253	69%	No

Latest Records

Latest records at Natrona Lock 4
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
11 October 2026	Natrona Lock 4, US	daily rain (Provisional)	26.9 mm (1.1 in)	10.1 mm (0.4 in)	56 years	37 of 100 (Notable)
4 September 2026	Natrona Lock 4, US	daily rain (Provisional)	49.5 mm (1.9 in)	13.4 mm (0.5 in)	84 years	45 of 100 (Notable)
3 August 2026	Natrona Lock 4, US	daily rain	62.2 mm (2.4 in)	12.7 mm (0.5 in)	45 years	33 of 100 (Routine)
23 May 2026	Natrona Lock 4, US	daily rain	25.9 mm (1.0 in)	1.0 mm (0.04 in)	72 years	32 of 100 (Routine)
27 March 2026	Natrona Lock 4, US	daily rain	34.3 mm (1.4 in)	12.5 mm (0.5 in)	68 years	46 of 100 (Notable)
23 March 2026	Natrona Lock 4, US	daily rain	39.4 mm (1.6 in)	21.6 mm (0.9 in)	76 years	60 of 100 (Major)
12 March 2026	Natrona Lock 4, US	daily rain	36.1 mm (1.4 in)	9.2 mm (0.36 in)	40 years	34 of 100 (Routine)
26 January 2026	Natrona Lock 4, US	daily snowfall	27.9 cm (11.0 in)	20.3 cm (8.0 in)	67 years	69 of 100 (Major)
26 January 2026	Natrona Lock 4, US	daily rain	27.9 mm (1.1 in)	5.8 mm (0.23 in)	92 years	45 of 100 (Notable)
14 December 2025	Natrona Lock 4, US	daily snowfall	14.0 cm (5.5 in)	3.8 cm (1.5 in)	22 years	24 of 100 (Routine)
3 December 2025	Natrona Lock 4, US	daily snowfall	8.9 cm (3.5 in)	2.5 cm (1.0 in)	88 years	40 of 100 (Notable)
17 July 2025	Natrona Lock 4, US	daily rain	78.7 mm (3.1 in)	36.8 mm (1.4 in)	88 years	64 of 100 (Major)
2 July 2025	Natrona Lock 4, US	daily rain	30.5 mm (1.2 in)	4.6 mm (0.18 in)	64 years	31 of 100 (Routine)
7 June 2025	Natrona Lock 4, US	daily rain (Tie)	50.0 mm (2.0 in)	tie	78 years	8 of 100 (Routine)
22 May 2025	Natrona Lock 4, US	daily rain	49.5 mm (1.9 in)	1.2 mm (0.05 in)	20 years	16 of 100 (Routine)
31 July 2024	Natrona Lock 4, US	daily rain	53.3 mm (2.1 in)	24.9 mm (1.0 in)	33 years	38 of 100 (Notable)
3 April 2024	Natrona Lock 4, US	daily rain	57.2 mm (2.3 in)	13.0 mm (0.5 in)	47 years	39 of 100 (Notable)
28 January 2024	Natrona Lock 4, US	daily rain	24.6 mm (1.0 in)	5.3 mm (0.21 in)	29 years	20 of 100 (Routine)
10 January 2024	Natrona Lock 4, US	daily rain	44.2 mm (1.7 in)	26.4 mm (1.0 in)	73 years	71 of 100 (Major)
22 November 2023	Natrona Lock 4, US	daily rain	28.7 mm (1.1 in)	5.8 mm (0.23 in)	70 years	37 of 100 (Notable)

Climate Trend

14 complete years, 2011 to 2025

One stripe for each of 14 complete years at Natrona Lock 4, 2011 to 2025. Blue stripes are years cooler than the station's own mean of 11.4 C (52.6 F); red stripes are warmer. The coolest year was 2014, at 10.0 C (49.9 F), and the warmest was 2024, at 12.7 C (54.9 F). The strongest colour marks a difference of 1.5 C (2.7 F).

Annual mean temperature at Natrona Lock 4 as warming stripes, 2011 to 2025
Year	Annual mean temperature	Difference from the station mean
2011	11.1 C	-0.32 C
2013	11.0 C	-0.42 C
2014	10.0 C	-1.49 C
2015	11.1 C	-0.31 C
2016	12.0 C	+0.51 C
2017	11.9 C	+0.46 C
2018	11.1 C	-0.40 C
2019	11.5 C	+0.02 C
2020	12.0 C	+0.59 C
2021	12.0 C	+0.52 C
2022	10.8 C	-0.61 C
2023	12.2 C	+0.75 C
2024	12.7 C	+1.25 C
2025	10.9 C	-0.58 C

This station does not have enough complete years (30 are needed) to fit a temperature trend.

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

1927 to 2026

Yearly extremes at Natrona Lock 4: 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)	1977	35.0 C (95.0 F)	18
Coldest night (TNn)	-24.4 C (-11.9 F)	2026	-18.0 C (-0.5 F)	18
Wettest day (Rx1day)	144.8 mm (5.7 in)	2004	49.2 mm (1.9 in)	100
Wettest five days (Rx5day)	176.8 mm (7.0 in)	2015	83.7 mm (3.3 in)	100
Longest dry spell (CDD)	31 days	1959	15 days	100

Hottest day (TXx)

The hottest day of the year at Natrona Lock 4, 1927 to 2026. The record is 40.0 C (104.0 F) in 1977, marked on the chart; the median year is 35.0 C (95.0 F).

Hottest day (TXx) at Natrona Lock 4 by year
Year	Hottest day (TXx)
1927	n/a
1928	n/a
1929	n/a
1930	n/a
1931	n/a
1932	n/a
1933	n/a
1934	n/a
1935	n/a
1936	n/a
1937	n/a
1938	n/a
1939	n/a
1940	n/a
1941	n/a
1942	n/a
1943	n/a
1944	n/a
1945	n/a
1946	n/a
1947	n/a
1948	n/a
1949	n/a
1950	n/a
1951	n/a
1952	n/a
1953	n/a
1954	n/a
1955	n/a
1956	n/a
1957	n/a
1958	n/a
1959	n/a
1960	n/a
1961	n/a
1962	n/a
1963	n/a
1964	n/a
1965	n/a
1966	n/a
1967	n/a
1968	n/a
1969	n/a
1970	n/a
1971	n/a
1972	n/a
1973	n/a
1974	n/a
1975	n/a
1976	n/a
1977	40.0 C (104.0 F)
1978	35.0 C (95.0 F)
1979	n/a
1980	n/a
1981	n/a
1982	n/a
1983	n/a
1984	n/a
1985	n/a
1986	n/a
1987	n/a
1988	n/a
1989	n/a
1990	n/a
1991	n/a
1992	n/a
1993	n/a
1994	n/a
1995	n/a
1996	n/a
1997	n/a
1998	n/a
1999	n/a
2000	n/a
2001	n/a
2002	n/a
2003	n/a
2004	n/a
2005	n/a
2006	n/a
2007	n/a
2008	n/a
2009	n/a
2010	n/a
2011	35.6 C (96.1 F)
2012	37.2 C (99.0 F)
2013	35.0 C (95.0 F)
2014	35.0 C (95.0 F)
2015	35.0 C (95.0 F)
2016	36.7 C (98.1 F)
2017	33.3 C (91.9 F)
2018	35.0 C (95.0 F)
2019	32.8 C (91.0 F)
2020	36.1 C (97.0 F)
2021	35.0 C (95.0 F)
2022	36.7 C (98.1 F)
2023	34.4 C (93.9 F)
2024	36.1 C (97.0 F)
2025	34.4 C (93.9 F)
2026	35.6 C (96.1 F)

Coldest night (TNn)

The coldest night of the year at Natrona Lock 4, 1927 to 2026. The record is -24.4 C (-11.9 F) in 2026, marked on the chart; the median year is -18.0 C (-0.5 F).

Coldest night (TNn) at Natrona Lock 4 by year
Year	Coldest night (TNn)
1927	n/a
1928	n/a
1929	n/a
1930	n/a
1931	n/a
1932	n/a
1933	n/a
1934	n/a
1935	n/a
1936	n/a
1937	n/a
1938	n/a
1939	n/a
1940	n/a
1941	n/a
1942	n/a
1943	n/a
1944	n/a
1945	n/a
1946	n/a
1947	n/a
1948	n/a
1949	n/a
1950	n/a
1951	n/a
1952	n/a
1953	n/a
1954	n/a
1955	n/a
1956	n/a
1957	n/a
1958	n/a
1959	n/a
1960	n/a
1961	n/a
1962	n/a
1963	n/a
1964	n/a
1965	n/a
1966	n/a
1967	n/a
1968	n/a
1969	n/a
1970	n/a
1971	n/a
1972	n/a
1973	n/a
1974	n/a
1975	n/a
1976	n/a
1977	11.1 C (52.0 F)
1978	4.4 C (39.9 F)
1979	n/a
1980	n/a
1981	n/a
1982	n/a
1983	n/a
1984	n/a
1985	n/a
1986	n/a
1987	n/a
1988	n/a
1989	n/a
1990	n/a
1991	n/a
1992	n/a
1993	n/a
1994	n/a
1995	n/a
1996	n/a
1997	n/a
1998	n/a
1999	n/a
2000	n/a
2001	n/a
2002	n/a
2003	n/a
2004	n/a
2005	n/a
2006	n/a
2007	n/a
2008	n/a
2009	n/a
2010	n/a
2011	-18.9 C (-2.0 F)
2012	-13.9 C (7.0 F)
2013	-13.9 C (7.0 F)
2014	-20.6 C (-5.1 F)
2015	-23.3 C (-9.9 F)
2016	-19.4 C (-2.9 F)
2017	-17.2 C (1.0 F)
2018	-20.6 C (-5.1 F)
2019	-19.4 C (-2.9 F)
2020	-12.2 C (10.0 F)
2021	-16.1 C (3.0 F)
2022	-22.2 C (-8.0 F)
2023	-12.8 C (9.0 F)
2024	-13.9 C (7.0 F)
2025	-21.7 C (-7.1 F)
2026	-24.4 C (-11.9 F)

Wettest day (Rx1day)

The wettest day of the year at Natrona Lock 4, 1927 to 2026. The record is 144.8 mm (5.7 in) in 2004, marked on the chart; the median year is 49.2 mm (1.9 in).

Wettest day (Rx1day) at Natrona Lock 4 by year
Year	Wettest day (Rx1day)
1927	29.2 mm (1.1 in)
1928	49.3 mm (1.9 in)
1929	67.1 mm (2.6 in)
1930	43.7 mm (1.7 in)
1931	49.0 mm (1.9 in)
1932	27.9 mm (1.1 in)
1933	47.8 mm (1.9 in)
1934	44.5 mm (1.8 in)
1935	85.9 mm (3.4 in)
1936	53.3 mm (2.1 in)
1937	83.6 mm (3.3 in)
1938	46.7 mm (1.8 in)
1939	35.8 mm (1.4 in)
1940	52.3 mm (2.1 in)
1941	57.2 mm (2.3 in)
1942	56.1 mm (2.2 in)
1943	40.9 mm (1.6 in)
1944	37.6 mm (1.5 in)
1945	40.9 mm (1.6 in)
1946	46.7 mm (1.8 in)
1947	50.0 mm (2.0 in)
1948	66.8 mm (2.6 in)
1949	29.7 mm (1.2 in)
1950	73.9 mm (2.9 in)
1951	46.0 mm (1.8 in)
1952	57.2 mm (2.3 in)
1953	51.3 mm (2.0 in)
1954	108.2 mm (4.3 in)
1955	42.7 mm (1.7 in)
1956	61.5 mm (2.4 in)
1957	47.8 mm (1.9 in)
1958	54.4 mm (2.1 in)
1959	44.5 mm (1.8 in)
1960	28.4 mm (1.1 in)
1961	34.3 mm (1.4 in)
1962	53.8 mm (2.1 in)
1963	44.7 mm (1.8 in)
1964	51.3 mm (2.0 in)
1965	41.1 mm (1.6 in)
1966	42.7 mm (1.7 in)
1967	57.2 mm (2.3 in)
1968	34.5 mm (1.4 in)
1969	48.3 mm (1.9 in)
1970	40.1 mm (1.6 in)
1971	54.6 mm (2.1 in)
1972	76.2 mm (3.0 in)
1973	37.6 mm (1.5 in)
1974	101.1 mm (4.0 in)
1975	47.8 mm (1.9 in)
1976	37.6 mm (1.5 in)
1977	49.3 mm (1.9 in)
1978	55.6 mm (2.2 in)
1979	46.5 mm (1.8 in)
1980	49.5 mm (1.9 in)
1981	86.4 mm (3.4 in)
1982	38.1 mm (1.5 in)
1983	35.6 mm (1.4 in)
1984	62.2 mm (2.4 in)
1985	116.6 mm (4.6 in)
1986	38.4 mm (1.5 in)
1987	78.2 mm (3.1 in)
1988	39.9 mm (1.6 in)
1989	34.5 mm (1.4 in)
1990	63.8 mm (2.5 in)
1991	46.0 mm (1.8 in)
1992	40.6 mm (1.6 in)
1993	42.7 mm (1.7 in)
1994	35.8 mm (1.4 in)
1995	27.9 mm (1.1 in)
1996	63.0 mm (2.5 in)
1997	49.3 mm (1.9 in)
1998	45.7 mm (1.8 in)
1999	74.7 mm (2.9 in)
2000	39.4 mm (1.6 in)
2001	45.0 mm (1.8 in)
2002	35.1 mm (1.4 in)
2003	53.3 mm (2.1 in)
2004	144.8 mm (5.7 in)
2005	47.5 mm (1.9 in)
2006	43.7 mm (1.7 in)
2007	74.4 mm (2.9 in)
2008	76.2 mm (3.0 in)
2009	47.0 mm (1.9 in)
2010	81.3 mm (3.2 in)
2011	48.5 mm (1.9 in)
2012	60.7 mm (2.4 in)
2013	60.2 mm (2.4 in)
2014	53.8 mm (2.1 in)
2015	86.4 mm (3.4 in)
2016	48.3 mm (1.9 in)
2017	114.8 mm (4.5 in)
2018	95.8 mm (3.8 in)
2019	99.1 mm (3.9 in)
2020	37.1 mm (1.5 in)
2021	68.6 mm (2.7 in)
2022	52.1 mm (2.1 in)
2023	47.0 mm (1.9 in)
2024	57.2 mm (2.3 in)
2025	78.7 mm (3.1 in)
2026	62.2 mm (2.4 in)

Wettest five days (Rx5day)

The wettest five days of the year at Natrona Lock 4, 1927 to 2026. The record is 176.8 mm (7.0 in) in 2015, marked on the chart; the median year is 83.7 mm (3.3 in).

Wettest five days (Rx5day) at Natrona Lock 4 by year
Year	Wettest five days (Rx5day)
1927	76.0 mm (3.0 in)
1928	75.7 mm (3.0 in)
1929	105.9 mm (4.2 in)
1930	75.5 mm (3.0 in)
1931	91.7 mm (3.6 in)
1932	46.9 mm (1.8 in)
1933	90.7 mm (3.6 in)
1934	83.3 mm (3.3 in)
1935	137.7 mm (5.4 in)
1936	119.2 mm (4.7 in)
1937	126.0 mm (5.0 in)
1938	98.3 mm (3.9 in)
1939	72.6 mm (2.9 in)
1940	79.5 mm (3.1 in)
1941	82.8 mm (3.3 in)
1942	91.6 mm (3.6 in)
1943	74.6 mm (2.9 in)
1944	56.9 mm (2.2 in)
1945	84.3 mm (3.3 in)
1946	66.1 mm (2.6 in)
1947	117.6 mm (4.6 in)
1948	128.2 mm (5.0 in)
1949	55.6 mm (2.2 in)
1950	111.0 mm (4.4 in)
1951	90.2 mm (3.6 in)
1952	93.3 mm (3.7 in)
1953	79.2 mm (3.1 in)
1954	128.8 mm (5.1 in)
1955	101.1 mm (4.0 in)
1956	101.8 mm (4.0 in)
1957	89.2 mm (3.5 in)
1958	70.7 mm (2.8 in)
1959	74.0 mm (2.9 in)
1960	77.0 mm (3.0 in)
1961	64.5 mm (2.5 in)
1962	80.3 mm (3.2 in)
1963	72.9 mm (2.9 in)
1964	83.7 mm (3.3 in)
1965	59.6 mm (2.3 in)
1966	67.2 mm (2.6 in)
1967	90.8 mm (3.6 in)
1968	61.1 mm (2.4 in)
1969	59.0 mm (2.3 in)
1970	61.5 mm (2.4 in)
1971	70.3 mm (2.8 in)
1972	166.5 mm (6.6 in)
1973	84.1 mm (3.3 in)
1974	113.6 mm (4.5 in)
1975	71.1 mm (2.8 in)
1976	56.6 mm (2.2 in)
1977	68.2 mm (2.7 in)
1978	85.3 mm (3.4 in)
1979	61.7 mm (2.4 in)
1980	62.2 mm (2.4 in)
1981	150.7 mm (5.9 in)
1982	84.2 mm (3.3 in)
1983	71.5 mm (2.8 in)
1984	71.3 mm (2.8 in)
1985	145.4 mm (5.7 in)
1986	58.9 mm (2.3 in)
1987	102.1 mm (4.0 in)
1988	71.8 mm (2.8 in)
1989	72.6 mm (2.9 in)
1990	89.9 mm (3.5 in)
1991	89.3 mm (3.5 in)
1992	70.0 mm (2.8 in)
1993	73.2 mm (2.9 in)
1994	67.1 mm (2.6 in)
1995	44.6 mm (1.8 in)
1996	82.6 mm (3.3 in)
1997	76.7 mm (3.0 in)
1998	78.0 mm (3.1 in)
1999	84.1 mm (3.3 in)
2000	50.4 mm (2.0 in)
2001	59.5 mm (2.3 in)
2002	54.8 mm (2.2 in)
2003	98.1 mm (3.9 in)
2004	148.6 mm (5.9 in)
2005	107.2 mm (4.2 in)
2006	83.6 mm (3.3 in)
2007	122.9 mm (4.8 in)
2008	85.8 mm (3.4 in)
2009	70.2 mm (2.8 in)
2010	88.7 mm (3.5 in)
2011	95.5 mm (3.8 in)
2012	95.5 mm (3.8 in)
2013	103.9 mm (4.1 in)
2014	109.4 mm (4.3 in)
2015	176.8 mm (7.0 in)
2016	78.5 mm (3.1 in)
2017	125.5 mm (4.9 in)
2018	161.9 mm (6.4 in)
2019	128.0 mm (5.0 in)
2020	76.0 mm (3.0 in)
2021	111.8 mm (4.4 in)
2022	107.7 mm (4.2 in)
2023	59.2 mm (2.3 in)
2024	96.7 mm (3.8 in)
2025	107.1 mm (4.2 in)
2026	88.4 mm (3.5 in)

Longest dry spell (CDD)

The longest dry spell of the year at Natrona Lock 4, 1927 to 2026. The record is 31 days in 1959, marked on the chart; the median year is 15 days.

Longest dry spell (CDD) at Natrona Lock 4 by year
Year	Longest dry spell (CDD)
1927	13 days
1928	13 days
1929	12 days
1930	13 days
1931	17 days
1932	16 days
1933	15 days
1934	17 days
1935	15 days
1936	11 days
1937	11 days
1938	20 days
1939	14 days
1940	14 days
1941	17 days
1942	15 days
1943	25 days
1944	13 days
1945	12 days
1946	22 days
1947	18 days
1948	17 days
1949	13 days
1950	12 days
1951	15 days
1952	19 days
1953	21 days
1954	12 days
1955	28 days
1956	16 days
1957	23 days
1958	16 days
1959	31 days
1960	11 days
1961	11 days
1962	18 days
1963	28 days
1964	26 days
1965	13 days
1966	15 days
1967	23 days
1968	10 days
1969	14 days
1970	15 days
1971	18 days
1972	10 days
1973	15 days
1974	16 days
1975	15 days
1976	13 days
1977	16 days
1978	11 days
1979	17 days
1980	16 days
1981	15 days
1982	17 days
1983	12 days
1984	10 days
1985	18 days
1986	16 days
1987	16 days
1988	31 days
1989	12 days
1990	12 days
1991	16 days
1992	15 days
1993	12 days
1994	17 days
1995	19 days
1996	11 days
1997	13 days
1998	18 days
1999	17 days
2000	16 days
2001	15 days
2002	11 days
2003	11 days
2004	12 days
2005	16 days
2006	17 days
2007	14 days
2008	12 days
2009	14 days
2010	16 days
2011	11 days
2012	13 days
2013	11 days
2014	11 days
2015	15 days
2016	15 days
2017	15 days
2018	11 days
2019	17 days
2020	14 days
2021	17 days
2022	9 days
2023	21 days
2024	19 days
2025	15 days
2026	11 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.

Rainfall Return Levels

97 years, 1928 to 2025

A day with at least 49.9 mm (2.0 in) of rain is expected about once in 2 years. A day with at least 141.2 mm (5.6 in) of rain is expected about once in 100 years.

Rainfall return levels at Natrona Lock 4: the daily rain expected about once in a given number of years
Expected about once in	A day with at least	Note
2 years	49.9 mm (2.0 in)
5 years	67.1 mm (2.6 in)
10 years	80.9 mm (3.2 in)
25 years	101.7 mm (4.0 in)
50 years	120.1 mm (4.7 in)
100 years	141.2 mm (5.6 in)	Longer than the 97 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, 97 years of values from 1928 to 2025.

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: 144.8 mm (5.7 in) in 2004; 116.6 mm (4.6 in) in 1985; 114.8 mm (4.5 in) in 2017.

Download the Data

Data for Natrona Lock 4 standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Natrona Lock 4 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 2026-10-12 (12 October 2026). Records are computed by this site and are not official.

Data as of 2026-10-13. Last revised 13 October 2026 (2026-10-13).