Groton Threshold Days by Year (USC00063207)

16 fixed thresholds counted per year at Groton (USC00063207): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Groton Thresholds

Groton: days with 10 mm (0.39 in) or more of precipitation in 63 years, most in 1983 with 59.
Groton: days with 25 mm (0.98 in) or more of precipitation in 63 years, most in 1953 with 23.
Groton: days with 50 mm (1.97 in) or more of precipitation in 58 years, most in 1970 with 7.
Groton: days with a maximum temperature at or above 30 C (86 F) in 52 years, most in 1983 with 36.
16 fixed thresholds have at least one qualifying day at Groton.

Days at or above 30 C (86 F)

52 years with a qualifying day

Days per year at Groton with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 36 in 1983.

Days at or above 30 C (86 F) per year at Groton
Year	Days	Decade average
1958	3	8
1959	13	8
1960	4	10.2
1961	12	10.2
1962	2	10.2
1963	13	10.2
1964	9	10.2
1965	15	10.2
1966	13	10.2
1967	2	10.2
1968	18	10.2
1969	14	10.2
1970	13	14.1
1971	12	14.1
1972	8	14.1
1973	19	14.1
1974	17	14.1
1975	16	14.1
1976	11	14.1
1977	22	14.1
1978	7	14.1
1979	16	14.1
1980	30	18.1
1981	14	18.1
1982	14	18.1
1983	36	18.1
1984	21	18.1
1985	13	18.1
1986	4	18.1
1987	13	18.1
1990	9	11.1
1991	35	11.1
1992	3	11.1
1993	10	11.1
1994	8	11.1
1995	14	11.1
1996	3	11.1
1997	9	11.1
1998	4	11.1
1999	16	11.1
2000	8	11.7
2001	10	11.7
2002	20	11.7
2003	16	11.7
2004	6	11.7
2008	10	11.7
2011	13	11
2015	7	11
2017	13	11
2020	15	12.3
2023	10	12.3
2024	12	12.3

For each year, a bar from the first to the last day at Groton meeting 30 C (86 F).

First to last qualifying date each year at Groton
Year	First date	Last date
1958	1958-07-02	1958-08-15
1959	1959-05-28	1959-09-09
1960	1960-08-03	1960-09-01
1961	1961-06-13	1961-09-12
1962	1962-06-01	1962-08-08
1963	1963-06-25	1963-07-29
1964	1964-05-23	1964-09-05
1965	1965-05-26	1965-08-18
1966	1966-06-24	1966-09-02
1967	1967-06-16	1967-07-31
1968	1968-06-06	1968-08-25
1969	1969-05-29	1969-09-02
1970	1970-07-27	1970-09-23
1971	1971-06-08	1971-09-09
1972	1972-07-12	1972-08-26
1973	1973-06-11	1973-09-04
1974	1974-05-17	1974-08-24
1975	1975-06-19	1975-08-22
1976	1976-06-08	1976-08-23
1977	1977-05-18	1977-09-02
1978	1978-06-28	1978-08-29
1979	1979-05-10	1979-08-06
1980	1980-06-24	1980-09-23
1981	1981-07-07	1981-09-14
1982	1982-07-08	1982-08-20
1983	1983-06-13	1983-09-20
1984	1984-06-07	1984-08-31
1985	1985-07-18	1985-09-08
1986	1986-05-30	1986-07-08
1987	1987-05-30	1987-08-18
1990	1990-07-05	1990-09-11
1991	1991-05-12	1991-09-17
1992	1992-05-22	1992-07-13
1993	1993-06-19	1993-08-26
1994	1994-06-19	1994-08-04
1995	1995-06-19	1995-08-21
1996	1996-05-20	1996-06-15
1997	1997-06-26	1997-08-17
1998	1998-06-26	1998-07-23
1999	1999-06-07	1999-08-01
2000	2000-06-09	2000-08-08
2001	2001-06-27	2001-08-09
2002	2002-04-17	2002-09-04
2003	2003-06-25	2003-09-11
2004	2004-06-08	2004-08-04
2008	2008-06-08	2008-08-25
2011	2011-06-08	2011-10-09
2015	2015-06-22	2015-09-08
2017	2017-05-18	2017-09-20
2020	2020-07-20	2020-09-03
2023	2023-07-12	2023-09-08
2024	2024-06-25	2024-08-28

Every Fixed Threshold

Fixed thresholds at Groton
Threshold	Years with a qualifying day	Most days in a year	Year	Latest year days
30 C (86 F): Days	52	36	1983	12
35 C (95 F): Days	11	4	1991	1
90 F (32.2 C): Days	41	14	1983	2
100 F (37.8 C): Days	1	1	1991	1
0 C (32 F): Ice days (max	52	38	1963	8
0 C (32 F): Frost days (min	52	148	1972	80
-10 C (14 F): Days with min	52	41	1968	4
-20 C (-4 F): Days with min	22	8	1961	1
20 C (68 F): Tropical nights (min	52	41	2020	34
25 C (77 F): Days with min	1	3	2020	3
10 mm (0.39 in): Days with 10 mm or more rain	63	59	1983	38
25 mm (0.98 in): Days with 25 mm or more rain	63	23	1953	17
50 mm (1.97 in): Days with 50 mm or more rain	58	7	1970	4
100 mm (3.94 in): Days with 100 mm or more rain	12	1	1952	1
10 cm (3.9 in): Days with 10 cm or more snowfall	46	6	1994	2
25 cm (9.8 in): Days with 25 cm or more snowfall	8	2	2017	2

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1958.

Download the Data

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 2026-10-17 (17 October 2026). Threshold counts are computed by this site.

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

Groton Threshold Days by Year (USC00063207)

Key Facts for Groton Thresholds

Days at or above 30 C (86 F)

Every Fixed Threshold

Download the Data

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