Groton Threshold Days by Year (USC00193270)

16 fixed thresholds counted per year at Groton (USC00193270): 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 57 years, most in 1897 with 47.
Groton: days with 25 mm (0.98 in) or more of precipitation in 57 years, most in 1901 with 21.
Groton: days with 50 mm (1.97 in) or more of precipitation in 44 years, most in 1895 with 4.
Groton: days with 10 cm (3.9 in) or more of snowfall in 19 years, most in 1967 with 10.
16 fixed thresholds have at least one qualifying day at Groton.

Days at or above 30 C (86 F)

16 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 27 in 1894.

Days at or above 30 C (86 F) per year at Groton
Year	Days	Decade average
1893	16	18.4
1894	27	18.4
1895	14	18.4
1896	26	18.4
1897	11	18.4
1898	17	18.4
1899	18	18.4
1900	23	14.9
1901	23	14.9
1902	7	14.9
1903	11	14.9
1904	9	14.9
1905	12	14.9
1906	10	14.9
1907	12	14.9
1908	27	14.9

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
1893	1893-05-23	1893-08-26
1894	1894-06-11	1894-09-10
1895	1895-05-04	1895-09-23
1896	1896-05-09	1896-09-11
1897	1897-07-05	1897-09-10
1898	1898-06-08	1898-09-04
1899	1899-05-01	1899-08-19
1900	1900-05-15	1900-09-12
1901	1901-06-06	1901-09-07
1902	1902-05-23	1902-09-01
1903	1903-05-18	1903-09-14
1904	1904-05-26	1904-08-01
1905	1905-06-16	1905-08-11
1906	1906-06-09	1906-09-19
1907	1907-06-18	1907-08-12
1908	1908-05-26	1908-09-11

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	16	27	1894	27
35 C (95 F): Days	4	2	1894	2
90 F (32.2 C): Days	15	13	1894	10
0 C (32 F): Ice days (max	16	82	1904	52
0 C (32 F): Frost days (min	16	176	1904	139
-10 C (14 F): Days with min	16	73	1904	49
-20 C (-4 F): Days with min	16	11	1904	7
20 C (68 F): Tropical nights (min	14	10	1901	3
25 C (77 F): Days with min	1	1	1900	1
10 mm (0.39 in): Days with 10 mm or more rain	57	47	1897	45
25 mm (0.98 in): Days with 25 mm or more rain	57	21	1901	10
50 mm (1.97 in): Days with 50 mm or more rain	44	4	1895	1
100 mm (3.94 in): Days with 100 mm or more rain	5	1	1927	1
10 cm (3.9 in): Days with 10 cm or more snowfall	19	10	1967	6
25 cm (9.8 in): Days with 25 cm or more snowfall	11	3	1961	1
50 cm (19.7 in): Days with 50 cm or more snowfall	1	1	1967	1

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1893.

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 (USC00193270)

Key Facts for Groton Thresholds

Days at or above 30 C (86 F)

Every Fixed Threshold

Download the Data

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