Groton Weather Records (USC00193270)

Record envelope, standing records and threshold days for Groton (USC00193270), Massachusetts, United States, with 82 years of record.

Key Facts for Groton

Groton (USC00193270) is a weather station in Massachusetts, United States at 42.60 latitude and -71.58 longitude, 104 m (341 ft) above sea level.
The station reports from 1893 to 1974, 82 years of record.
1,464 records set at Groton still stand.
Records are tracked for prcp, snow: an element needs 30 years of data to be eligible.
Groton set a daily record precipitation of 74.7 mm (2.9 in) on 8 October 1972.

About the Station

Location: Massachusetts, United States, 42.60 latitude, -71.58 longitude.
Elevation: 104 m (341 ft).
Period of record: 1893 to 1974, 82 years.
Eligible elements: prcp, snow.

Daily Record Envelope and 2026

0 days at or beyond a record

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	16.7 C (62.1 F)	-27.2 C (-17.0 F)	n/a	n/a
Feb	14.4 C (57.9 F)	-27.2 C (-17.0 F)	n/a	n/a
Mar	23.9 C (75.0 F)	-22.2 C (-8.0 F)	n/a	n/a
Apr	28.3 C (82.9 F)	-10.0 C (14.0 F)	n/a	n/a
May	32.8 C (91.0 F)	-4.4 C (24.1 F)	n/a	n/a
Jun	35.0 C (95.0 F)	1.7 C (35.1 F)	n/a	n/a
Jul	36.1 C (97.0 F)	5.0 C (41.0 F)	n/a	n/a
Aug	34.4 C (93.9 F)	0.6 C (33.1 F)	n/a	n/a
Sep	33.3 C (91.9 F)	-3.9 C (25.0 F)	n/a	n/a
Oct	29.4 C (84.9 F)	-8.9 C (16.0 F)	n/a	n/a
Nov	22.2 C (72.0 F)	-15.6 C (3.9 F)	n/a	n/a
Dec	17.2 C (63.0 F)	-25.6 C (-14.1 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Groton still stand. 1896 holds the most, with 127.

Wettest Day of Each Month

Nov: 169.4 mm (6.7 in)

The wettest day on record for each calendar month at Groton. The most was 169.4 mm (6.7 in) on 3 November 1927.

Record daily precipitation for each month at Groton
Month	Record daily precipitation (mm)	Date
Jan	56.4 mm (2.2 in)	14 January 1940
Feb	66.3 mm (2.6 in)	6 February 1896
Mar	85.9 mm (3.4 in)	1 March 1900
Apr	56.1 mm (2.2 in)	3 April 1901
May	73.7 mm (2.9 in)	4 May 1893
Jun	111.0 mm (4.4 in)	24 June 1944
Jul	103.9 mm (4.1 in)	21 July 1959
Aug	77.2 mm (3.0 in)	5 August 1969
Sep	139.7 mm (5.5 in)	16 September 1932
Oct	90.9 mm (3.6 in)	6 October 1962
Nov	169.4 mm (6.7 in)	3 November 1927
Dec	82.8 mm (3.3 in)	27 December 1969

Period of Record Coverage

1893 to 1908

16 years of record at Groton, 1893 to 1908. 1 years have data for under 90 percent of days and are left out of rankings: 1908.

Days with data per year at Groton
Year	Days with data	Share of year	Complete
1893	353	97%	Yes
1894	354	97%	Yes
1895	348	95%	Yes
1896	349	95%	Yes
1897	356	98%	Yes
1898	356	98%	Yes
1899	355	97%	Yes
1900	351	96%	Yes
1901	344	94%	Yes
1902	346	95%	Yes
1903	351	96%	Yes
1904	358	98%	Yes
1905	360	99%	Yes
1906	363	99%	Yes
1907	355	97%	Yes
1908	329	90%	No

Latest Records

Latest records at Groton
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
8 October 1972	Groton, US	daily rain	74.7 mm (2.9 in)	26.4 mm (1.0 in)	65 years	47 of 100 (Notable)
20 July 1972	Groton, US	daily rain	57.4 mm (2.3 in)	2.0 mm (0.08 in)	21 years	15 of 100 (Routine)
14 July 1972	Groton, US	daily rain	57.9 mm (2.3 in)	29.7 mm (1.2 in)	24 years	43 of 100 (Notable)
9 July 1972	Groton, US	daily rain	54.4 mm (2.1 in)	38.9 mm (1.5 in)	71 years	66 of 100 (Major)
4 July 1972	Groton, US	daily rain	24.4 mm (1.0 in)	2.6 mm (0.10 in)	2 years	10 of 100 (Routine)
5 June 1972	Groton, US	daily rain	19.8 mm (0.8 in)	6.1 mm (0.24 in)	74 years	20 of 100 (Routine)
1 June 1972	Groton, US	daily rain	59.2 mm (2.3 in)	33.3 mm (1.3 in)	10 years	40 of 100 (Notable)
3 March 1972	Groton, US	daily rain	26.9 mm (1.1 in)	3.0 mm (0.12 in)	66 years	29 of 100 (Routine)
25 November 1971	Groton, US	daily snowfall	12.7 cm (5.0 in)	10.2 cm (4.0 in)	76 years	43 of 100 (Notable)
22 November 1971	Groton, US	daily snowfall	15.2 cm (6.0 in)	10.1 cm (4.0 in)	77 years	43 of 100 (Notable)
22 June 1971	Groton, US	daily rain	40.6 mm (1.6 in)	2.5 mm (0.10 in)	70 years	30 of 100 (Routine)
17 April 1971	Groton, US	daily snowfall	2.5 cm (1.0 in)	2.5 cm (1.0 in)	77 years	20 of 100 (Routine)
7 April 1971	Groton, US	daily snowfall	12.7 cm (5.0 in)	7.6 cm (3.0 in)	71 years	37 of 100 (Notable)
4 March 1971	Groton, US	daily rain	29.0 mm (1.1 in)	1.6 mm (0.06 in)	30 years	17 of 100 (Routine)
18 December 1970	Groton, US	daily rain	14.5 mm (0.6 in)	3.1 mm (0.12 in)	40 years	20 of 100 (Routine)
17 December 1970	Groton, US	daily snowfall	25.4 cm (10.0 in)	24.1 cm (9.5 in)	70 years	57 of 100 (Notable)
17 December 1970	Groton, US	daily rain	22.9 mm (0.9 in)	0.5 mm (0.02 in)	9 years	9 of 100 (Routine)
24 October 1970	Groton, US	daily rain	53.8 mm (2.1 in)	8.6 mm (0.34 in)	44 years	26 of 100 (Routine)
4 October 1970	Groton, US	daily rain	20.1 mm (0.8 in)	6.4 mm (0.25 in)	63 years	20 of 100 (Routine)
4 July 1970	Groton, US	daily rain	21.8 mm (0.9 in)	4.3 mm (0.17 in)	41 years	20 of 100 (Routine)

Climate Trend

15 complete years, 1893 to 1907

One stripe for each of 15 complete years at Groton, 1893 to 1907. Blue stripes are years cooler than the station's own mean of 7.6 C (45.7 F); red stripes are warmer. The coolest year was 1904, at 6.2 C (43.2 F), and the warmest was 1898, at 8.3 C (46.9 F). The strongest colour marks a difference of 1.4 C (2.5 F).

Annual mean temperature at Groton as warming stripes, 1893 to 1907
Year	Annual mean temperature	Difference from the station mean
1893	6.8 C	-0.77 C
1894	8.2 C	+0.56 C
1895	7.7 C	+0.06 C
1896	7.7 C	+0.06 C
1897	7.9 C	+0.30 C
1898	8.3 C	+0.68 C
1899	7.8 C	+0.21 C
1900	8.2 C	+0.55 C
1901	7.8 C	+0.19 C
1902	8.0 C	+0.41 C
1903	7.9 C	+0.31 C
1904	6.2 C	-1.40 C
1905	7.1 C	-0.50 C
1906	7.7 C	+0.09 C
1907	6.9 C	-0.75 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

1893 to 1974

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)	36.1 C (97.0 F)	1908	33.6 C (92.5 F)	16
Coldest night (TNn)	-27.2 C (-17.0 F)	1894	-25.0 C (-13.0 F)	16
Wettest day (Rx1day)	169.4 mm (6.7 in)	1927	58.7 mm (2.3 in)	65
Wettest five days (Rx5day)	179.3 mm (7.1 in)	1962	85.2 mm (3.4 in)	65
Longest dry spell (CDD)	36 days	1947	16 days	65

Hottest day (TXx)

The hottest day of the year at Groton, 1893 to 1974. The record is 36.1 C (97.0 F) in 1908, marked on the chart; the median year is 33.6 C (92.5 F).

Hottest day (TXx) at Groton by year
Year	Hottest day (TXx)
1893	32.2 C (90.0 F)
1894	35.0 C (95.0 F)
1895	33.3 C (91.9 F)
1896	33.9 C (93.0 F)
1897	34.4 C (93.9 F)
1898	35.0 C (95.0 F)
1899	32.8 C (91.0 F)
1900	34.4 C (93.9 F)
1901	35.6 C (96.1 F)
1902	31.7 C (89.1 F)
1903	33.3 C (91.9 F)
1904	32.8 C (91.0 F)
1905	33.3 C (91.9 F)
1906	32.2 C (90.0 F)
1907	33.9 C (93.0 F)
1908	36.1 C (97.0 F)
1925	n/a
1926	n/a
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
1974	n/a

Coldest night (TNn)

The coldest night of the year at Groton, 1893 to 1974. The record is -27.2 C (-17.0 F) in 1894, marked on the chart; the median year is -25.0 C (-13.0 F).

Coldest night (TNn) at Groton by year
Year	Coldest night (TNn)
1893	-25.6 C (-14.1 F)
1894	-27.2 C (-17.0 F)
1895	-23.9 C (-11.0 F)
1896	-26.7 C (-16.1 F)
1897	-20.0 C (-4.0 F)
1898	-25.6 C (-14.1 F)
1899	-27.2 C (-17.0 F)
1900	-21.7 C (-7.1 F)
1901	-23.9 C (-11.0 F)
1902	-25.6 C (-14.1 F)
1903	-24.4 C (-11.9 F)
1904	-26.7 C (-16.1 F)
1905	-23.3 C (-9.9 F)
1906	-21.1 C (-6.0 F)
1907	-25.6 C (-14.1 F)
1908	-24.4 C (-11.9 F)
1925	n/a
1926	n/a
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
1974	n/a

Wettest day (Rx1day)

The wettest day of the year at Groton, 1893 to 1974. The record is 169.4 mm (6.7 in) in 1927, marked on the chart; the median year is 58.7 mm (2.3 in).

Wettest day (Rx1day) at Groton by year
Year	Wettest day (Rx1day)
1893	73.7 mm (2.9 in)
1894	46.5 mm (1.8 in)
1895	88.4 mm (3.5 in)
1896	75.7 mm (3.0 in)
1897	58.4 mm (2.3 in)
1898	70.6 mm (2.8 in)
1899	46.2 mm (1.8 in)
1900	85.9 mm (3.4 in)
1901	61.5 mm (2.4 in)
1902	69.6 mm (2.7 in)
1903	89.2 mm (3.5 in)
1904	69.3 mm (2.7 in)
1905	68.6 mm (2.7 in)
1906	54.6 mm (2.1 in)
1907	79.0 mm (3.1 in)
1908	49.5 mm (1.9 in)
1925	44.7 mm (1.8 in)
1926	62.2 mm (2.4 in)
1927	169.4 mm (6.7 in)
1928	71.1 mm (2.8 in)
1929	43.7 mm (1.7 in)
1930	37.3 mm (1.5 in)
1931	57.4 mm (2.3 in)
1932	139.7 mm (5.5 in)
1933	69.6 mm (2.7 in)
1934	93.5 mm (3.7 in)
1935	57.9 mm (2.3 in)
1936	65.8 mm (2.6 in)
1937	67.8 mm (2.7 in)
1938	59.2 mm (2.3 in)
1939	50.8 mm (2.0 in)
1940	56.4 mm (2.2 in)
1941	52.1 mm (2.1 in)
1942	57.7 mm (2.3 in)
1943	45.2 mm (1.8 in)
1944	111.0 mm (4.4 in)
1945	43.2 mm (1.7 in)
1946	71.9 mm (2.8 in)
1947	50.0 mm (2.0 in)
1948	37.6 mm (1.5 in)
1949	35.3 mm (1.4 in)
1950	78.2 mm (3.1 in)
1951	62.5 mm (2.5 in)
1952	66.5 mm (2.6 in)
1953	52.6 mm (2.1 in)
1954	122.4 mm (4.8 in)
1955	72.1 mm (2.8 in)
1956	42.2 mm (1.7 in)
1957	47.2 mm (1.9 in)
1958	51.6 mm (2.0 in)
1959	103.9 mm (4.1 in)
1960	74.9 mm (2.9 in)
1961	40.6 mm (1.6 in)
1962	90.9 mm (3.6 in)
1963	58.7 mm (2.3 in)
1964	44.5 mm (1.8 in)
1965	37.8 mm (1.5 in)
1966	50.8 mm (2.0 in)
1967	55.4 mm (2.2 in)
1968	49.3 mm (1.9 in)
1969	82.8 mm (3.3 in)
1970	53.8 mm (2.1 in)
1971	41.7 mm (1.6 in)
1972	74.7 mm (2.9 in)
1974	13.5 mm (0.5 in)

Wettest five days (Rx5day)

The wettest five days of the year at Groton, 1893 to 1974. The record is 179.3 mm (7.1 in) in 1962, marked on the chart; the median year is 85.2 mm (3.4 in).

Wettest five days (Rx5day) at Groton by year
Year	Wettest five days (Rx5day)
1893	99.6 mm (3.9 in)
1894	66.8 mm (2.6 in)
1895	158.8 mm (6.3 in)
1896	98.3 mm (3.9 in)
1897	100.6 mm (4.0 in)
1898	84.3 mm (3.3 in)
1899	63.0 mm (2.5 in)
1900	121.2 mm (4.8 in)
1901	157.7 mm (6.2 in)
1902	70.6 mm (2.8 in)
1903	133.7 mm (5.3 in)
1904	110.5 mm (4.4 in)
1905	141.8 mm (5.6 in)
1906	111.5 mm (4.4 in)
1907	99.3 mm (3.9 in)
1908	49.7 mm (2.0 in)
1925	61.6 mm (2.4 in)
1926	66.0 mm (2.6 in)
1927	170.5 mm (6.7 in)
1928	80.8 mm (3.2 in)
1929	68.1 mm (2.7 in)
1930	66.3 mm (2.6 in)
1931	89.7 mm (3.5 in)
1932	144.8 mm (5.7 in)
1933	162.3 mm (6.4 in)
1934	98.3 mm (3.9 in)
1935	118.3 mm (4.7 in)
1936	101.7 mm (4.0 in)
1937	77.4 mm (3.0 in)
1938	147.3 mm (5.8 in)
1939	85.2 mm (3.4 in)
1940	92.5 mm (3.6 in)
1941	55.1 mm (2.2 in)
1942	72.7 mm (2.9 in)
1943	66.8 mm (2.6 in)
1944	159.2 mm (6.3 in)
1945	61.8 mm (2.4 in)
1946	84.6 mm (3.3 in)
1947	94.7 mm (3.7 in)
1948	66.0 mm (2.6 in)
1949	44.8 mm (1.8 in)
1950	88.7 mm (3.5 in)
1951	101.4 mm (4.0 in)
1952	72.3 mm (2.8 in)
1953	82.6 mm (3.3 in)
1954	150.4 mm (5.9 in)
1955	159.4 mm (6.3 in)
1956	80.6 mm (3.2 in)
1957	80.0 mm (3.1 in)
1958	60.2 mm (2.4 in)
1959	129.3 mm (5.1 in)
1960	119.7 mm (4.7 in)
1961	76.7 mm (3.0 in)
1962	179.3 mm (7.1 in)
1963	99.8 mm (3.9 in)
1964	61.7 mm (2.4 in)
1965	46.0 mm (1.8 in)
1966	76.7 mm (3.0 in)
1967	62.7 mm (2.5 in)
1968	86.1 mm (3.4 in)
1969	111.5 mm (4.4 in)
1970	78.1 mm (3.1 in)
1971	69.0 mm (2.7 in)
1972	80.5 mm (3.2 in)
1974	24.7 mm (1.0 in)

Longest dry spell (CDD)

The longest dry spell of the year at Groton, 1893 to 1974. The record is 36 days in 1947, marked on the chart; the median year is 16 days.

Longest dry spell (CDD) at Groton by year
Year	Longest dry spell (CDD)
1893	15 days
1894	23 days
1895	21 days
1896	16 days
1897	15 days
1898	10 days
1899	9 days
1900	19 days
1901	14 days
1902	14 days
1903	16 days
1904	17 days
1905	23 days
1906	17 days
1907	11 days
1908	22 days
1925	15 days
1926	15 days
1927	15 days
1928	12 days
1929	12 days
1930	17 days
1931	13 days
1932	20 days
1933	12 days
1934	19 days
1935	20 days
1936	14 days
1937	13 days
1938	12 days
1939	25 days
1940	18 days
1941	19 days
1942	13 days
1943	23 days
1944	16 days
1945	17 days
1946	18 days
1947	36 days
1948	12 days
1949	22 days
1950	16 days
1951	13 days
1952	20 days
1953	17 days
1954	18 days
1955	24 days
1956	14 days
1957	19 days
1958	21 days
1959	15 days
1960	18 days
1961	17 days
1962	13 days
1963	24 days
1964	21 days
1965	19 days
1966	15 days
1967	12 days
1968	21 days
1969	16 days
1970	13 days
1971	14 days
1972	13 days
1974	6 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

57 years, 1893 to 1971

A day with at least 60.1 mm (2.4 in) of rain is expected about once in 2 years. A day with at least 163.4 mm (6.4 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	60.1 mm (2.4 in)
5 years	80.4 mm (3.2 in)
10 years	96.4 mm (3.8 in)
25 years	120.0 mm (4.7 in)
50 years	140.4 mm (5.5 in)
100 years	163.4 mm (6.4 in)	Longer than the 57 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, 57 years of values from 1893 to 1971.

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: 169.4 mm (6.7 in) in 1927; 139.7 mm (5.5 in) in 1932; 122.4 mm (4.8 in) in 1954.

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.

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