Record envelope, standing records and threshold days for Groton (USC00063207), Connecticut, United States, with 77 years of record.
Key Facts for Groton
Groton (USC00063207) is a weather station in Connecticut, United States at 41.35 latitude and -72.04 longitude, 12 m (40 ft) above sea level.
The station reports from 1948 to 2024, 77 years of record.
1,464 records set at Groton still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Groton set a daily record high minimum temperature of 8.9 C (48.0 F) on 30 December 2024.
About the Station
Location: Connecticut, United States, 41.35 latitude, -72.04 longitude.
Elevation: 12 m (40 ft).
Period of record: 1948 to 2024, 77 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 Groton. 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 Groton, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
20.6 C (69.1 F)
-25.6 C (-14.1 F)
n/a
n/a
Feb
21.1 C (70.0 F)
-24.4 C (-11.9 F)
n/a
n/a
Mar
25.6 C (78.1 F)
-17.8 C (0.0 F)
n/a
n/a
Apr
31.1 C (88.0 F)
-10.0 C (14.0 F)
n/a
n/a
May
32.8 C (91.0 F)
-1.1 C (30.0 F)
n/a
n/a
Jun
35.0 C (95.0 F)
3.3 C (37.9 F)
n/a
n/a
Jul
38.3 C (100.9 F)
8.3 C (46.9 F)
n/a
n/a
Aug
37.2 C (99.0 F)
5.0 C (41.0 F)
n/a
n/a
Sep
33.9 C (93.0 F)
-1.7 C (28.9 F)
n/a
n/a
Oct
30.6 C (87.1 F)
-5.6 C (21.9 F)
n/a
n/a
Nov
26.1 C (79.0 F)
-13.3 C (8.1 F)
n/a
n/a
Dec
20.6 C (69.1 F)
-23.3 C (-9.9 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Groton still stand. 1962 holds the most, with 38.
Standing records at Groton by the year they were set
Year set
Standing records
1957
24
1958
32
1959
31
1960
23
1961
33
1962
38
1963
38
1964
32
1965
27
1966
21
1967
35
1968
21
1969
15
1970
18
1971
15
1972
24
1973
17
1974
28
1975
24
1976
35
1977
24
1978
23
1979
34
1980
17
1981
23
1982
21
1983
15
1984
24
1985
23
1986
24
1987
19
1988
23
1989
20
1990
33
1991
33
1992
20
1993
21
1994
14
1995
27
1996
23
1997
11
1998
17
1999
9
2000
25
2001
22
2002
34
2003
14
2004
9
2005
1
2007
17
2008
18
2009
11
2010
33
2011
21
2012
22
2013
4
2014
8
2015
35
2016
22
2017
34
2018
25
2019
6
2020
20
2021
17
2023
17
2024
20
All-Time Record Progression
5 new records
5 all-time records were set at Groton between 20 January 1987 and 27 January 2015. Each dot is a new record.
When Groton set new all-time records
Date
Kind
Detail
1987-01-20
Record snow depth
Record snow depth 61.0 cm (24.0 in)
1991-07-21
Record high maximum temperature
Record high maximum temperature 38.3 C (100.9 F)
2001-07-25
Record high minimum temperature
Record high minimum temperature 25.6 C (78.1 F)
2015-01-27
Record daily snowfall
Record daily snowfall 61.0 cm (24.0 in)
2015-01-27
Record snow depth
Record snow depth 66.0 cm (26.0 in)
Wettest Day of Each Month
Sep: 188.7 mm (7.4 in)
The wettest day on record for each calendar month at Groton. The most was 188.7 mm (7.4 in) on 21 September 1961.
Record daily precipitation for each month at Groton
Month
Record daily precipitation (mm)
Date
Jan
72.6 mm (2.9 in)
6 January 1962
Feb
72.6 mm (2.9 in)
13 February 2008
Mar
80.0 mm (3.1 in)
26 March 1988
Apr
83.6 mm (3.3 in)
13 April 2004
May
89.2 mm (3.5 in)
25 May 1967
Jun
160.0 mm (6.3 in)
5 June 1982
Jul
111.3 mm (4.4 in)
1 July 2009
Aug
130.6 mm (5.1 in)
12 August 1955
Sep
188.7 mm (7.4 in)
21 September 1961
Oct
122.4 mm (4.8 in)
5 October 1962
Nov
86.1 mm (3.4 in)
5 November 1985
Dec
93.5 mm (3.7 in)
3 December 1986
Period of Record Coverage
1957 to 2024
Complete yearUnder 90 percent of days
66 years of record at Groton, 1957 to 2024. 14 years have data for under 90 percent of days and are left out of rankings: 1957, 1988, 1989, 2005, 2007, 2009, 2010, 2012 and others.
Cooler than the station meanWarmer than the station mean
One stripe for each of 45 complete years at Groton, 1958 to 2024. Blue stripes are years cooler than the station's own mean of 10.1 C (50.3 F); red stripes are warmer. The coolest year was 1958, at 8.7 C (47.7 F), and the warmest was 2024, at 12.2 C (53.9 F). The strongest colour marks a difference of 2.1 C (3.8 F).
Annual mean temperature at Groton as warming stripes, 1958 to 2024
Year
Annual mean temperature
Difference from the station mean
1958
8.7 C
-1.40 C
1959
10.0 C
-0.14 C
1960
9.6 C
-0.52 C
1961
9.7 C
-0.47 C
1962
8.9 C
-1.26 C
1963
9.3 C
-0.89 C
1964
9.6 C
-0.55 C
1965
9.5 C
-0.68 C
1966
9.7 C
-0.47 C
1967
9.2 C
-0.96 C
1968
9.7 C
-0.46 C
1969
9.9 C
-0.22 C
1970
9.6 C
-0.55 C
1971
10.0 C
-0.12 C
1972
9.2 C
-0.94 C
1973
10.5 C
+0.34 C
1974
10.1 C
-0.09 C
1975
10.5 C
+0.34 C
1976
9.6 C
-0.54 C
1977
9.9 C
-0.29 C
1978
9.0 C
-1.13 C
1979
10.3 C
+0.11 C
1980
10.1 C
-0.08 C
1981
10.0 C
-0.14 C
1982
10.3 C
+0.18 C
1983
11.0 C
+0.82 C
1984
10.8 C
+0.62 C
1985
10.5 C
+0.40 C
1986
10.2 C
+0.06 C
1987
10.2 C
+0.05 C
1990
11.1 C
+0.93 C
1991
11.4 C
+1.27 C
1993
10.1 C
-0.08 C
1994
9.9 C
-0.20 C
1995
10.2 C
+0.08 C
1996
9.5 C
-0.62 C
1997
9.9 C
-0.22 C
1999
10.7 C
+0.56 C
2000
9.9 C
-0.23 C
2002
11.9 C
+1.72 C
2003
10.6 C
+0.42 C
2004
10.7 C
+0.59 C
2008
11.3 C
+1.20 C
2011
11.8 C
+1.62 C
2024
12.2 C
+2.03 C
The annual mean temperature here has risen by 0.4 C (0.3 to 0.5) per decade over 1958 to 2024. In Fahrenheit: 0.7 F (0.5 to 0.8) per decade. The slope is a straight line fitted to 45 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at Groton
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
0.4 C (0.3 to 0.5) per decade
0.7 F (0.5 to 0.8) per decade
1958 to 2024
45
Rise
Mean daily maximum
0.2 C (0.1 to 0.3) per decade
0.3 F (0.1 to 0.5) per decade
1958 to 2024
45
Rise
Mean daily minimum
0.6 C (0.5 to 0.7) per decade
1.0 F (0.8 to 1.2) per decade
1958 to 2024
45
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
1948 to 2024
Yearly extremes at Groton: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
38.3 C (100.9 F)
1991
33.1 C (91.5 F)
66
Coldest night (TNn)
-25.6 C (-14.1 F)
1961
-18.0 C (-0.5 F)
66
Wettest day (Rx1day)
188.7 mm (7.4 in)
1961
68.3 mm (2.7 in)
75
Wettest five days (Rx5day)
297.1 mm (11.7 in)
1982
105.2 mm (4.1 in)
75
Longest dry spell (CDD)
39 days
1949
17 days
75
Hottest day (TXx)
The hottest day of the year at Groton, 1948 to 2024. The record is 38.3 C (100.9 F) in 1991, marked on the chart; the median year is 33.1 C (91.5 F).
Hottest day (TXx) at Groton by year
Year
Hottest day (TXx)
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
35.0 C (95.0 F)
1958
31.1 C (88.0 F)
1959
32.2 C (90.0 F)
1960
31.1 C (88.0 F)
1961
32.2 C (90.0 F)
1962
31.1 C (88.0 F)
1963
34.4 C (93.9 F)
1964
35.0 C (95.0 F)
1965
33.3 C (91.9 F)
1966
36.1 C (97.0 F)
1967
31.7 C (89.1 F)
1968
33.9 C (93.0 F)
1969
34.4 C (93.9 F)
1970
32.8 C (91.0 F)
1971
32.8 C (91.0 F)
1972
32.2 C (90.0 F)
1973
33.3 C (91.9 F)
1974
32.8 C (91.0 F)
1975
37.2 C (99.0 F)
1976
32.2 C (90.0 F)
1977
37.2 C (99.0 F)
1978
33.3 C (91.9 F)
1979
35.6 C (96.1 F)
1980
36.7 C (98.1 F)
1981
34.4 C (93.9 F)
1982
34.4 C (93.9 F)
1983
34.4 C (93.9 F)
1984
33.3 C (91.9 F)
1985
33.3 C (91.9 F)
1986
31.7 C (89.1 F)
1987
33.3 C (91.9 F)
1988
32.8 C (91.0 F)
1989
31.1 C (88.0 F)
1990
31.7 C (89.1 F)
1991
38.3 C (100.9 F)
1992
30.6 C (87.1 F)
1993
34.4 C (93.9 F)
1994
33.3 C (91.9 F)
1995
35.0 C (95.0 F)
1996
31.7 C (89.1 F)
1997
31.7 C (89.1 F)
1998
32.8 C (91.0 F)
1999
36.7 C (98.1 F)
2000
34.4 C (93.9 F)
2001
34.4 C (93.9 F)
2002
35.6 C (96.1 F)
2003
32.2 C (90.0 F)
2004
31.1 C (88.0 F)
2005
14.4 C (57.9 F)
2007
31.7 C (89.1 F)
2008
32.8 C (91.0 F)
2009
32.2 C (90.0 F)
2010
36.7 C (98.1 F)
2011
36.1 C (97.0 F)
2012
32.8 C (91.0 F)
2013
31.7 C (89.1 F)
2014
30.6 C (87.1 F)
2015
32.2 C (90.0 F)
2016
33.3 C (91.9 F)
2017
32.8 C (91.0 F)
2018
33.3 C (91.9 F)
2019
33.9 C (93.0 F)
2020
33.3 C (91.9 F)
2021
32.2 C (90.0 F)
2023
32.2 C (90.0 F)
2024
31.7 C (89.1 F)
Coldest night (TNn)
The coldest night of the year at Groton, 1948 to 2024. The record is -25.6 C (-14.1 F) in 1961, marked on the chart; the median year is -18.0 C (-0.5 F).
Coldest night (TNn) at Groton by year
Year
Coldest night (TNn)
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
-11.1 C (12.0 F)
1958
-19.4 C (-2.9 F)
1959
-16.7 C (1.9 F)
1960
-16.1 C (3.0 F)
1961
-25.6 C (-14.1 F)
1962
-23.3 C (-9.9 F)
1963
-21.1 C (-6.0 F)
1964
-15.6 C (3.9 F)
1965
-24.4 C (-11.9 F)
1966
-16.1 C (3.0 F)
1967
-22.8 C (-9.0 F)
1968
-22.2 C (-8.0 F)
1969
-15.6 C (3.9 F)
1970
-20.0 C (-4.0 F)
1971
-19.4 C (-2.9 F)
1972
-17.2 C (1.0 F)
1973
-17.8 C (0.0 F)
1974
-18.3 C (-0.9 F)
1975
-16.7 C (1.9 F)
1976
-20.0 C (-4.0 F)
1977
-20.0 C (-4.0 F)
1978
-23.3 C (-9.9 F)
1979
-23.9 C (-11.0 F)
1980
-23.3 C (-9.9 F)
1981
-23.9 C (-11.0 F)
1982
-25.0 C (-13.0 F)
1983
-18.3 C (-0.9 F)
1984
-23.9 C (-11.0 F)
1985
-17.2 C (1.0 F)
1986
-17.2 C (1.0 F)
1987
-17.8 C (0.0 F)
1988
-20.6 C (-5.1 F)
1989
-21.7 C (-7.1 F)
1990
-16.1 C (3.0 F)
1991
-21.1 C (-6.0 F)
1992
-15.6 C (3.9 F)
1993
-18.9 C (-2.0 F)
1994
-20.6 C (-5.1 F)
1995
-17.8 C (0.0 F)
1996
-22.8 C (-9.0 F)
1997
-18.3 C (-0.9 F)
1998
-12.8 C (9.0 F)
1999
-16.7 C (1.9 F)
2000
-17.2 C (1.0 F)
2001
-14.4 C (6.1 F)
2002
-11.1 C (12.0 F)
2003
-20.0 C (-4.0 F)
2004
-19.4 C (-2.9 F)
2005
-18.3 C (-0.9 F)
2007
-15.6 C (3.9 F)
2008
-13.3 C (8.1 F)
2009
-21.1 C (-6.0 F)
2010
-14.4 C (6.1 F)
2011
-17.2 C (1.0 F)
2012
-11.7 C (10.9 F)
2013
-9.4 C (15.1 F)
2014
-13.9 C (7.0 F)
2015
-20.6 C (-5.1 F)
2016
-22.2 C (-8.0 F)
2017
-12.2 C (10.0 F)
2018
-10.6 C (12.9 F)
2019
-17.2 C (1.0 F)
2020
-11.7 C (10.9 F)
2021
-12.8 C (9.0 F)
2023
-21.1 C (-6.0 F)
2024
-13.3 C (8.1 F)
Wettest day (Rx1day)
The wettest day of the year at Groton, 1948 to 2024. The record is 188.7 mm (7.4 in) in 1961, marked on the chart; the median year is 68.3 mm (2.7 in).
Wettest day (Rx1day) at Groton by year
Year
Wettest day (Rx1day)
1948
41.7 mm (1.6 in)
1949
47.2 mm (1.9 in)
1950
36.1 mm (1.4 in)
1951
84.3 mm (3.3 in)
1952
121.9 mm (4.8 in)
1953
69.1 mm (2.7 in)
1954
156.2 mm (6.1 in)
1955
130.6 mm (5.1 in)
1956
53.3 mm (2.1 in)
1957
51.8 mm (2.0 in)
1958
72.1 mm (2.8 in)
1959
68.6 mm (2.7 in)
1960
82.3 mm (3.2 in)
1961
188.7 mm (7.4 in)
1962
122.4 mm (4.8 in)
1963
52.1 mm (2.1 in)
1964
52.8 mm (2.1 in)
1965
34.5 mm (1.4 in)
1966
58.2 mm (2.3 in)
1967
89.2 mm (3.5 in)
1968
65.0 mm (2.6 in)
1969
68.6 mm (2.7 in)
1970
76.2 mm (3.0 in)
1971
113.8 mm (4.5 in)
1972
124.5 mm (4.9 in)
1973
85.9 mm (3.4 in)
1974
53.1 mm (2.1 in)
1975
59.4 mm (2.3 in)
1976
60.5 mm (2.4 in)
1977
69.3 mm (2.7 in)
1978
48.5 mm (1.9 in)
1979
67.1 mm (2.6 in)
1980
54.6 mm (2.1 in)
1981
52.3 mm (2.1 in)
1982
160.0 mm (6.3 in)
1983
77.5 mm (3.1 in)
1984
60.7 mm (2.4 in)
1985
107.4 mm (4.2 in)
1986
93.5 mm (3.7 in)
1987
55.9 mm (2.2 in)
1988
84.8 mm (3.3 in)
1989
99.1 mm (3.9 in)
1990
119.4 mm (4.7 in)
1991
116.1 mm (4.6 in)
1992
74.4 mm (2.9 in)
1993
75.7 mm (3.0 in)
1994
65.5 mm (2.6 in)
1995
87.1 mm (3.4 in)
1996
65.5 mm (2.6 in)
1997
40.6 mm (1.6 in)
1998
88.4 mm (3.5 in)
1999
88.1 mm (3.5 in)
2000
65.3 mm (2.6 in)
2001
120.7 mm (4.8 in)
2002
51.1 mm (2.0 in)
2003
61.7 mm (2.4 in)
2004
83.6 mm (3.3 in)
2005
18.0 mm (0.7 in)
2007
66.3 mm (2.6 in)
2008
97.3 mm (3.8 in)
2009
111.3 mm (4.4 in)
2010
48.3 mm (1.9 in)
2011
70.9 mm (2.8 in)
2012
36.1 mm (1.4 in)
2013
45.5 mm (1.8 in)
2014
62.5 mm (2.5 in)
2015
58.4 mm (2.3 in)
2016
55.1 mm (2.2 in)
2017
68.3 mm (2.7 in)
2018
52.3 mm (2.1 in)
2019
67.6 mm (2.7 in)
2020
53.3 mm (2.1 in)
2021
50.8 mm (2.0 in)
2023
74.9 mm (2.9 in)
2024
85.1 mm (3.4 in)
Wettest five days (Rx5day)
The wettest five days of the year at Groton, 1948 to 2024. The record is 297.1 mm (11.7 in) in 1982, marked on the chart; the median year is 105.2 mm (4.1 in).
Wettest five days (Rx5day) at Groton by year
Year
Wettest five days (Rx5day)
1948
55.5 mm (2.2 in)
1949
66.0 mm (2.6 in)
1950
53.1 mm (2.1 in)
1951
122.9 mm (4.8 in)
1952
184.0 mm (7.2 in)
1953
117.1 mm (4.6 in)
1954
169.4 mm (6.7 in)
1955
160.1 mm (6.3 in)
1956
70.4 mm (2.8 in)
1957
99.1 mm (3.9 in)
1958
113.5 mm (4.5 in)
1959
127.4 mm (5.0 in)
1960
105.0 mm (4.1 in)
1961
202.2 mm (8.0 in)
1962
131.1 mm (5.2 in)
1963
76.5 mm (3.0 in)
1964
97.5 mm (3.8 in)
1965
57.2 mm (2.3 in)
1966
70.3 mm (2.8 in)
1967
109.0 mm (4.3 in)
1968
101.9 mm (4.0 in)
1969
109.5 mm (4.3 in)
1970
148.1 mm (5.8 in)
1971
123.7 mm (4.9 in)
1972
171.7 mm (6.8 in)
1973
88.4 mm (3.5 in)
1974
64.8 mm (2.6 in)
1975
99.6 mm (3.9 in)
1976
105.7 mm (4.2 in)
1977
87.4 mm (3.4 in)
1978
73.9 mm (2.9 in)
1979
129.9 mm (5.1 in)
1980
124.5 mm (4.9 in)
1981
75.2 mm (3.0 in)
1982
297.1 mm (11.7 in)
1983
105.2 mm (4.1 in)
1984
123.3 mm (4.9 in)
1985
177.5 mm (7.0 in)
1986
110.5 mm (4.4 in)
1987
97.0 mm (3.8 in)
1988
144.1 mm (5.7 in)
1989
141.7 mm (5.6 in)
1990
125.0 mm (4.9 in)
1991
144.6 mm (5.7 in)
1992
92.1 mm (3.6 in)
1993
83.8 mm (3.3 in)
1994
108.7 mm (4.3 in)
1995
94.2 mm (3.7 in)
1996
114.0 mm (4.5 in)
1997
66.6 mm (2.6 in)
1998
137.4 mm (5.4 in)
1999
112.9 mm (4.4 in)
2000
81.3 mm (3.2 in)
2001
120.7 mm (4.8 in)
2002
83.6 mm (3.3 in)
2003
81.3 mm (3.2 in)
2004
97.1 mm (3.8 in)
2005
41.2 mm (1.6 in)
2007
107.2 mm (4.2 in)
2008
114.5 mm (4.5 in)
2009
119.7 mm (4.7 in)
2010
107.7 mm (4.2 in)
2011
117.4 mm (4.6 in)
2012
66.5 mm (2.6 in)
2013
54.9 mm (2.2 in)
2014
96.1 mm (3.8 in)
2015
85.8 mm (3.4 in)
2016
72.7 mm (2.9 in)
2017
150.6 mm (5.9 in)
2018
83.8 mm (3.3 in)
2019
88.4 mm (3.5 in)
2020
65.1 mm (2.6 in)
2021
83.5 mm (3.3 in)
2023
92.3 mm (3.6 in)
2024
129.8 mm (5.1 in)
Longest dry spell (CDD)
The longest dry spell of the year at Groton, 1948 to 2024. The record is 39 days in 1949, marked on the chart; the median year is 17 days.
Longest dry spell (CDD) at Groton by year
Year
Longest dry spell (CDD)
1948
23 days
1949
39 days
1950
11 days
1951
12 days
1952
22 days
1953
19 days
1954
13 days
1955
16 days
1956
23 days
1957
17 days
1958
21 days
1959
16 days
1960
18 days
1961
15 days
1962
16 days
1963
28 days
1964
19 days
1965
37 days
1966
15 days
1967
16 days
1968
22 days
1969
17 days
1970
15 days
1971
17 days
1972
12 days
1973
16 days
1974
16 days
1975
15 days
1976
20 days
1977
17 days
1978
19 days
1979
21 days
1980
24 days
1981
17 days
1982
21 days
1983
22 days
1984
20 days
1985
17 days
1986
18 days
1987
23 days
1988
16 days
1989
14 days
1990
12 days
1991
13 days
1992
17 days
1993
13 days
1994
17 days
1995
37 days
1996
11 days
1997
17 days
1998
16 days
1999
23 days
2000
11 days
2001
17 days
2002
17 days
2003
23 days
2004
25 days
2005
4 days
2007
20 days
2008
17 days
2009
14 days
2010
14 days
2011
16 days
2012
14 days
2013
23 days
2014
17 days
2015
19 days
2016
15 days
2017
12 days
2018
13 days
2019
14 days
2020
19 days
2021
17 days
2023
20 days
2024
24 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
45 years with a frost
Across 45 years with a frost, the median last spring frost at Groton falls on 19 April and the median first autumn frost on 21 October, which leaves a median of 185 days between them.
Fitted over all years, the growing season changes by +7.0 days per decade at this station.
Frost dates and growing season at Groton
Measure
Median, all years
Earliest period
Recent period (1973 to 2024)
Recent against earliest
Fitted trend
Last spring frost
19 April
n/a
14 April
n/a
-4.5 days per decade
First autumn frost
21 October
n/a
22 October
n/a
+2.5 days per decade
Growing days
185 days
n/a
191 days
n/a
+7.0 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
63 years, 1949 to 2024
A day with at least 72.5 mm (2.9 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 Groton: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
72.5 mm (2.9 in)
5 years
99.0 mm (3.9 in)
10 years
118.9 mm (4.7 in)
25 years
146.8 mm (5.8 in)
50 years
169.8 mm (6.7 in)
100 years
194.8 mm (7.7 in)
Longer than the 63 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, 63 years of values from 1949 to 2024.
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: 188.7 mm (7.4 in) in 1961; 160.0 mm (6.3 in) in 1982; 156.2 mm (6.1 in) in 1954.
Station Changes
No change in the annual mean temperature of this station was found against its neighbours.
Download the Data
Data for Groton standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Groton 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 2026-10-14 (14 October 2026). Records are computed by this site and are not official.