Hurricanes and Tornadoes That Hit Groton, CT

The nearest NOAA station with 1991–2020 climate normals is Groton, CT, in Groton at 40 feet. July is the warmest, with an average high of 81°F and low of 66°F; January is the coolest, at 39°F and 24°F. March is the wettest at 4.9 inches of precipitation on average and February and July the driest at 3.4 inches; the year adds up to 48.9 inches over 81 days with at least a tenth of an inch. June to November, the hurricane season months, bring 49% of the year's precipitation (24.0 of 48.9 inches); the other six months are wetter. September has brought the most of the 58 tropical systems that passed within 75 miles (24); a normal September there has highs of 74°F and 4.3 inches of precipitation. Highs reach 90°F on about 3 days a year, almost all from July. Lows fall below freezing on about 101 nights a year. Snowfall averages 24.5 inches a year, most of it in February. That 48.9 inches is more than at 11 of the 27 Connecticut stations used on this site (41%). New London, 3 miles west, has its own station (Groton New London Airport, CT): 39.2 inches a year, 9.7 less than here, and a July average high of 80°F against 81°F.

Water temperature at the NOAA tide station New London, CT, 3 miles northwest, averaged 71°F in August and 39°F in February over 2021–2025. No month averaged 80°F. Sea level at the New London tide gauge, 3 miles from Groton, has risen 1.16 ± 0.04 inches per decade from 1938 to 2025, NOAA's linear trend; at that pace it is 11.6 inches in a hundred years. That is faster than at 66 of the 144 U.S. gauges with a NOAA trend.

Since 1996, the National Weather Service has logged 83 flood, rain, thunderstorm wind and lightning events that began within 10 miles of Groton: 42 flash floods, 30 thunderstorm wind reports, 8 floods, 2 lightning strikes and 1 heavy rain event. They killed 2 people and injured 2, and the NWS estimated $1.8 million in property and crop damage. The strongest thunderstorm gust on record here was 70 mph, on July 19, 2010. July has had the most flash floods, 18 of 42. Of the 186 Connecticut cities on this site with a flash flood on record, 122 have had fewer than Groton.

Flood insurance policyholders in Groton's ZIP code 06340 have filed 339 claims with the National Flood Insurance Program since 1978, and were paid $4.1 million for buildings and contents, in the dollars of each year. The most came from Hurricane Sandy in 2012: 180 claims (53% of all) and $3.5 million, then March 2010 Nor'easter in 2010 with 24 and Not a named storm in 1982 with 24. 77% of the claims carry the name of a storm or flood event; the rest have no event name. Of the 128 Connecticut cities on this site with 10 or more claims, 106 have fewer than Groton.