Record envelope, standing records and threshold days for Knightville Dam (USC00193985), Massachusetts, United States, with 50 years of record.
Key Facts for Knightville Dam
Knightville Dam (USC00193985) is a weather station in Massachusetts, United States at 42.28 latitude and -72.87 longitude, 192 m (630 ft) above sea level.
The station reports from 1948 to 1997, 50 years of record.
1,464 records set at Knightville Dam still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Knightville Dam set a daily record precipitation of 32.3 mm (1.3 in) on 20 May 1997.
About the Station
Location: Massachusetts, United States, 42.28 latitude, -72.87 longitude.
Elevation: 192 m (630 ft).
Period of record: 1948 to 1997, 50 years.
Eligible elements: tmax, tmin, prcp, snow, snwd.
Daily Record Envelope and 2026
0 days at or beyond a record
Record highRecord low2026 daily maximum2026 daily minimum
The band shows the record high and record low for each calendar day at Knightville Dam. 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 Knightville Dam, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
16.7 C (62.1 F)
-31.1 C (-24.0 F)
n/a
n/a
Feb
20.6 C (69.1 F)
-31.7 C (-25.1 F)
n/a
n/a
Mar
28.3 C (82.9 F)
-26.1 C (-15.0 F)
n/a
n/a
Apr
33.3 C (91.9 F)
-12.2 C (10.0 F)
n/a
n/a
May
33.9 C (93.0 F)
-5.0 C (23.0 F)
n/a
n/a
Jun
37.2 C (99.0 F)
0.0 C (32.0 F)
n/a
n/a
Jul
37.2 C (99.0 F)
4.4 C (39.9 F)
n/a
n/a
Aug
37.8 C (100.0 F)
-0.6 C (30.9 F)
n/a
n/a
Sep
37.8 C (100.0 F)
-5.6 C (21.9 F)
n/a
n/a
Oct
31.1 C (88.0 F)
-9.4 C (15.1 F)
n/a
n/a
Nov
27.2 C (81.0 F)
-21.1 C (-6.0 F)
n/a
n/a
Dec
18.9 C (66.0 F)
-28.3 C (-18.9 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Knightville Dam still stand. 1949 holds the most, with 53.
Standing records at Knightville Dam by the year they were set
Year set
Standing records
1948
14
1949
53
1950
30
1951
49
1952
28
1953
48
1954
34
1955
43
1956
49
1957
53
1958
26
1959
44
1960
29
1961
39
1962
23
1963
41
1964
36
1965
31
1966
31
1967
36
1968
33
1969
22
1970
28
1971
29
1972
23
1973
22
1974
25
1975
17
1976
44
1977
32
1978
26
1979
43
1980
12
1981
30
1982
27
1983
20
1984
28
1985
17
1986
22
1987
29
1988
26
1989
31
1990
35
1991
29
1992
26
1993
20
1994
9
1995
10
1996
10
1997
2
All-Time Record Progression
2 new records
2 all-time records were set at Knightville Dam between 26 December 1980 and 10 July 1981. Each dot is a new record.
When Knightville Dam set new all-time records
Date
Kind
Detail
1980-12-26
Record low maximum temperature
Record low maximum temperature -20.6 C (-5.1 F)
1981-07-10
Record high minimum temperature
Record high minimum temperature 21.7 C (71.1 F)
Wettest Day of Each Month
Aug: 215.9 mm (8.5 in)
The wettest day on record for each calendar month at Knightville Dam. The most was 215.9 mm (8.5 in) on 19 August 1955.
Record daily precipitation for each month at Knightville Dam
Month
Record daily precipitation (mm)
Date
Jan
76.2 mm (3.0 in)
25 January 1979
Feb
67.3 mm (2.6 in)
21 February 1981
Mar
106.7 mm (4.2 in)
22 March 1980
Apr
94.0 mm (3.7 in)
20 April 1983
May
64.5 mm (2.5 in)
30 May 1984
Jun
123.2 mm (4.9 in)
6 June 1982
Jul
98.6 mm (3.9 in)
14 July 1996
Aug
215.9 mm (8.5 in)
19 August 1955
Sep
151.1 mm (5.9 in)
28 September 1985
Oct
133.4 mm (5.3 in)
15 October 1955
Nov
79.8 mm (3.1 in)
23 November 1952
Dec
95.3 mm (3.8 in)
31 December 1948
Period of Record Coverage
1948 to 1997
Complete yearUnder 90 percent of days
50 years of record at Knightville Dam, 1948 to 1997. 8 years have data for under 90 percent of days and are left out of rankings: 1948, 1991, 1992, 1993, 1994, 1995, 1996, 1997.
Cooler than the station meanWarmer than the station mean
One stripe for each of 41 complete years at Knightville Dam, 1949 to 1990. Blue stripes are years cooler than the station's own mean of 7.5 C (45.6 F); red stripes are warmer. The coolest year was 1962, at 6.4 C (43.6 F), and the warmest was 1951, at 9.2 C (48.5 F). The strongest colour marks a difference of 1.7 C (3.1 F).
Annual mean temperature at Knightville Dam as warming stripes, 1949 to 1990
Year
Annual mean temperature
Difference from the station mean
1949
8.4 C
+0.91 C
1951
9.2 C
+1.63 C
1952
8.8 C
+1.31 C
1953
9.2 C
+1.62 C
1954
8.1 C
+0.55 C
1955
8.2 C
+0.67 C
1956
7.2 C
-0.36 C
1957
8.0 C
+0.50 C
1958
6.6 C
-0.93 C
1959
8.1 C
+0.56 C
1960
7.0 C
-0.51 C
1961
7.1 C
-0.44 C
1962
6.4 C
-1.10 C
1963
6.5 C
-1.05 C
1964
6.9 C
-0.59 C
1965
7.0 C
-0.57 C
1966
7.4 C
-0.14 C
1967
7.1 C
-0.48 C
1968
7.3 C
-0.20 C
1969
7.5 C
-0.01 C
1970
7.2 C
-0.34 C
1971
7.2 C
-0.31 C
1972
6.8 C
-0.73 C
1973
8.6 C
+1.08 C
1974
7.5 C
-0.06 C
1975
7.9 C
+0.39 C
1976
7.0 C
-0.58 C
1977
7.3 C
-0.25 C
1978
6.4 C
-1.10 C
1979
7.7 C
+0.19 C
1980
7.1 C
-0.44 C
1981
7.7 C
+0.20 C
1982
7.3 C
-0.26 C
1983
8.0 C
+0.49 C
1984
7.8 C
+0.29 C
1985
7.4 C
-0.10 C
1986
7.4 C
-0.11 C
1987
7.6 C
+0.08 C
1988
7.2 C
-0.31 C
1989
6.9 C
-0.62 C
1990
8.6 C
+1.09 C
The fitted trend in annual mean temperature here over 1949 to 1990 is -0.14 C (-0.33 to 0.04) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: -0.3 F (-0.6 to 0.1) per decade. The slope is a straight line fitted to 41 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at Knightville Dam
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
-0.14 C (-0.33 to 0.04) per decade
-0.3 F (-0.6 to 0.1) per decade
1949 to 1990
41
Not clearly different from zero
Mean daily maximum
-0.19 C (-0.39 to 0.02) per decade
-0.33 F (-0.70 to 0.03) per decade
1949 to 1990
41
Not clearly different from zero
Mean daily minimum
-0.1 C (-0.3 to 0.1) per decade
-0.2 F (-0.5 to 0.2) per decade
1949 to 1990
41
Not clearly different from zero
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
1948 to 1997
Yearly extremes at Knightville Dam: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
37.8 C (100.0 F)
1948
34.4 C (93.9 F)
50
Coldest night (TNn)
-31.7 C (-25.1 F)
1971
-25.6 C (-14.1 F)
50
Wettest day (Rx1day)
215.9 mm (8.5 in)
1955
64.4 mm (2.5 in)
50
Wettest five days (Rx5day)
269.4 mm (10.6 in)
1955
103.9 mm (4.1 in)
50
Longest dry spell (CDD)
26 days
1968
16 days
50
Hottest day (TXx)
The hottest day of the year at Knightville Dam, 1948 to 1997. The record is 37.8 C (100.0 F) in 1948, marked on the chart; the median year is 34.4 C (93.9 F).
Hottest day (TXx) at Knightville Dam by year
Year
Hottest day (TXx)
1948
37.8 C (100.0 F)
1949
35.6 C (96.1 F)
1950
34.4 C (93.9 F)
1951
32.8 C (91.0 F)
1952
37.2 C (99.0 F)
1953
37.8 C (100.0 F)
1954
34.4 C (93.9 F)
1955
37.8 C (100.0 F)
1956
35.0 C (95.0 F)
1957
35.0 C (95.0 F)
1958
32.8 C (91.0 F)
1959
33.9 C (93.0 F)
1960
31.1 C (88.0 F)
1961
32.2 C (90.0 F)
1962
33.9 C (93.0 F)
1963
34.4 C (93.9 F)
1964
34.4 C (93.9 F)
1965
35.0 C (95.0 F)
1966
36.1 C (97.0 F)
1967
34.4 C (93.9 F)
1968
35.0 C (95.0 F)
1969
33.9 C (93.0 F)
1970
32.8 C (91.0 F)
1971
34.4 C (93.9 F)
1972
33.3 C (91.9 F)
1973
33.9 C (93.0 F)
1974
35.0 C (95.0 F)
1975
36.1 C (97.0 F)
1976
33.3 C (91.9 F)
1977
35.0 C (95.0 F)
1978
32.2 C (90.0 F)
1979
33.9 C (93.0 F)
1980
34.4 C (93.9 F)
1981
33.3 C (91.9 F)
1982
35.0 C (95.0 F)
1983
34.4 C (93.9 F)
1984
34.4 C (93.9 F)
1985
32.2 C (90.0 F)
1986
32.8 C (91.0 F)
1987
33.9 C (93.0 F)
1988
36.1 C (97.0 F)
1989
32.2 C (90.0 F)
1990
32.8 C (91.0 F)
1991
36.1 C (97.0 F)
1992
33.3 C (91.9 F)
1993
35.6 C (96.1 F)
1994
32.8 C (91.0 F)
1995
33.9 C (93.0 F)
1996
32.8 C (91.0 F)
1997
15.6 C (60.1 F)
Coldest night (TNn)
The coldest night of the year at Knightville Dam, 1948 to 1997. The record is -31.7 C (-25.1 F) in 1971, marked on the chart; the median year is -25.6 C (-14.1 F).
Coldest night (TNn) at Knightville Dam by year
Year
Coldest night (TNn)
1948
-22.8 C (-9.0 F)
1949
-22.8 C (-9.0 F)
1950
-25.6 C (-14.1 F)
1951
-28.3 C (-18.9 F)
1952
-22.8 C (-9.0 F)
1953
-17.8 C (0.0 F)
1954
-25.6 C (-14.1 F)
1955
-25.0 C (-13.0 F)
1956
-22.2 C (-8.0 F)
1957
-31.1 C (-24.0 F)
1958
-26.7 C (-16.1 F)
1959
-23.3 C (-9.9 F)
1960
-25.6 C (-14.1 F)
1961
-31.1 C (-24.0 F)
1962
-28.9 C (-20.0 F)
1963
-28.9 C (-20.0 F)
1964
-24.4 C (-11.9 F)
1965
-26.1 C (-15.0 F)
1966
-25.0 C (-13.0 F)
1967
-26.1 C (-15.0 F)
1968
-30.6 C (-23.1 F)
1969
-23.3 C (-9.9 F)
1970
-26.7 C (-16.1 F)
1971
-31.7 C (-25.1 F)
1972
-26.7 C (-16.1 F)
1973
-22.8 C (-9.0 F)
1974
-23.3 C (-9.9 F)
1975
-23.3 C (-9.9 F)
1976
-28.9 C (-20.0 F)
1977
-28.9 C (-20.0 F)
1978
-26.1 C (-15.0 F)
1979
-26.7 C (-16.1 F)
1980
-28.3 C (-18.9 F)
1981
-28.3 C (-18.9 F)
1982
-29.4 C (-20.9 F)
1983
-22.8 C (-9.0 F)
1984
-30.0 C (-22.0 F)
1985
-25.6 C (-14.1 F)
1986
-20.6 C (-5.1 F)
1987
-25.6 C (-14.1 F)
1988
-27.2 C (-17.0 F)
1989
-26.7 C (-16.1 F)
1990
-21.7 C (-7.1 F)
1991
-22.8 C (-9.0 F)
1992
-19.4 C (-2.9 F)
1993
-22.2 C (-8.0 F)
1994
-30.6 C (-23.1 F)
1995
-24.4 C (-11.9 F)
1996
-26.7 C (-16.1 F)
1997
-15.6 C (3.9 F)
Wettest day (Rx1day)
The wettest day of the year at Knightville Dam, 1948 to 1997. The record is 215.9 mm (8.5 in) in 1955, marked on the chart; the median year is 64.4 mm (2.5 in).
Wettest day (Rx1day) at Knightville Dam by year
Year
Wettest day (Rx1day)
1948
95.3 mm (3.8 in)
1949
43.2 mm (1.7 in)
1950
61.0 mm (2.4 in)
1951
54.6 mm (2.1 in)
1952
79.8 mm (3.1 in)
1953
68.6 mm (2.7 in)
1954
57.2 mm (2.3 in)
1955
215.9 mm (8.5 in)
1956
36.8 mm (1.4 in)
1957
44.5 mm (1.8 in)
1958
44.5 mm (1.8 in)
1959
55.9 mm (2.2 in)
1960
92.7 mm (3.6 in)
1961
61.0 mm (2.4 in)
1962
43.2 mm (1.7 in)
1963
47.0 mm (1.9 in)
1964
41.9 mm (1.6 in)
1965
54.9 mm (2.2 in)
1966
62.2 mm (2.4 in)
1967
58.4 mm (2.3 in)
1968
63.5 mm (2.5 in)
1969
87.4 mm (3.4 in)
1970
57.9 mm (2.3 in)
1971
94.2 mm (3.7 in)
1972
64.8 mm (2.6 in)
1973
66.0 mm (2.6 in)
1974
55.9 mm (2.2 in)
1975
68.6 mm (2.7 in)
1976
80.0 mm (3.1 in)
1977
61.0 mm (2.4 in)
1978
57.2 mm (2.3 in)
1979
76.2 mm (3.0 in)
1980
106.7 mm (4.2 in)
1981
67.3 mm (2.6 in)
1982
123.2 mm (4.9 in)
1983
94.0 mm (3.7 in)
1984
67.3 mm (2.6 in)
1985
151.1 mm (5.9 in)
1986
68.6 mm (2.7 in)
1987
86.4 mm (3.4 in)
1988
61.0 mm (2.4 in)
1989
70.6 mm (2.8 in)
1990
75.4 mm (3.0 in)
1991
64.0 mm (2.5 in)
1992
86.4 mm (3.4 in)
1993
54.9 mm (2.2 in)
1994
60.5 mm (2.4 in)
1995
79.5 mm (3.1 in)
1996
98.6 mm (3.9 in)
1997
38.1 mm (1.5 in)
Wettest five days (Rx5day)
The wettest five days of the year at Knightville Dam, 1948 to 1997. The record is 269.4 mm (10.6 in) in 1955, marked on the chart; the median year is 103.9 mm (4.1 in).
Wettest five days (Rx5day) at Knightville Dam by year
Year
Wettest five days (Rx5day)
1948
128.3 mm (5.1 in)
1949
128.3 mm (5.1 in)
1950
90.0 mm (3.5 in)
1951
105.4 mm (4.1 in)
1952
91.2 mm (3.6 in)
1953
102.4 mm (4.0 in)
1954
118.7 mm (4.7 in)
1955
269.4 mm (10.6 in)
1956
61.6 mm (2.4 in)
1957
61.7 mm (2.4 in)
1958
73.5 mm (2.9 in)
1959
96.6 mm (3.8 in)
1960
129.5 mm (5.1 in)
1961
83.4 mm (3.3 in)
1962
61.7 mm (2.4 in)
1963
85.2 mm (3.4 in)
1964
49.5 mm (1.9 in)
1965
61.8 mm (2.4 in)
1966
74.3 mm (2.9 in)
1967
84.4 mm (3.3 in)
1968
94.8 mm (3.7 in)
1969
117.2 mm (4.6 in)
1970
99.6 mm (3.9 in)
1971
124.4 mm (4.9 in)
1972
86.9 mm (3.4 in)
1973
114.3 mm (4.5 in)
1974
77.2 mm (3.0 in)
1975
160.1 mm (6.3 in)
1976
135.9 mm (5.4 in)
1977
98.6 mm (3.9 in)
1978
78.0 mm (3.1 in)
1979
148.7 mm (5.9 in)
1980
130.9 mm (5.2 in)
1981
125.7 mm (4.9 in)
1982
160.5 mm (6.3 in)
1983
143.5 mm (5.6 in)
1984
202.3 mm (8.0 in)
1985
176.3 mm (6.9 in)
1986
86.4 mm (3.4 in)
1987
128.5 mm (5.1 in)
1988
148.3 mm (5.8 in)
1989
129.0 mm (5.1 in)
1990
129.6 mm (5.1 in)
1991
124.4 mm (4.9 in)
1992
88.9 mm (3.5 in)
1993
123.0 mm (4.8 in)
1994
102.2 mm (4.0 in)
1995
91.7 mm (3.6 in)
1996
132.2 mm (5.2 in)
1997
29.7 mm (1.2 in)
Longest dry spell (CDD)
The longest dry spell of the year at Knightville Dam, 1948 to 1997. The record is 26 days in 1968, marked on the chart; the median year is 16 days.
Longest dry spell (CDD) at Knightville Dam by year
Year
Longest dry spell (CDD)
1948
25 days
1949
16 days
1950
17 days
1951
16 days
1952
21 days
1953
25 days
1954
13 days
1955
24 days
1956
16 days
1957
18 days
1958
15 days
1959
14 days
1960
13 days
1961
13 days
1962
14 days
1963
23 days
1964
20 days
1965
15 days
1966
20 days
1967
21 days
1968
26 days
1969
16 days
1970
14 days
1971
15 days
1972
16 days
1973
14 days
1974
13 days
1975
16 days
1976
17 days
1977
14 days
1978
14 days
1979
18 days
1980
23 days
1981
18 days
1982
16 days
1983
20 days
1984
19 days
1985
18 days
1986
14 days
1987
18 days
1988
20 days
1989
13 days
1990
19 days
1991
14 days
1992
11 days
1993
12 days
1994
18 days
1995
16 days
1996
15 days
1997
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
41 years with a frost
Across 41 years with a frost, the median last spring frost at Knightville Dam falls on 17 May and the median first autumn frost on 23 September, which leaves a median of 129 days between them.
Fitted over all years, the growing season changes by +3.4 days per decade at this station.
Frost dates and growing season at Knightville Dam
Measure
Median, all years
Earliest period
Recent period (1961 to 1990)
Recent against earliest
Fitted trend
Last spring frost
17 May
n/a
16 May
n/a
-3.5 days per decade
First autumn frost
23 September
n/a
22 September
n/a
-0.1 days per decade
Growing days
129 days
n/a
130 days
n/a
+3.4 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
46 years, 1949 to 1996
A day with at least 64.2 mm (2.5 in) of rain is expected about once in 2 years. A day with at least 194.8 mm (7.7 in) of rain is expected about once in 100 years.
Rainfall return levels at Knightville Dam: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
64.2 mm (2.5 in)
5 years
86.3 mm (3.4 in)
10 years
105.0 mm (4.1 in)
25 years
134.7 mm (5.3 in)
50 years
162.1 mm (6.4 in)
Longer than the 46 years of record
100 years
194.8 mm (7.7 in)
Longer than the 46 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, 46 years of values from 1949 to 1996.
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: 215.9 mm (8.5 in) in 1955; 151.1 mm (5.9 in) in 1985; 123.2 mm (4.9 in) in 1982.
Station Changes
No change in the annual mean temperature of this station was found against its neighbours.
Download the Data
Data for Knightville Dam standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Knightville Dam 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.