Groton

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond this area.
2. Weak tornadoes were under-recorded before Doppler radar coverage became national in the early 1990s, so earlier decades read low. Ratings use the Fujita scale before February 2007 and the Enhanced Fujita scale after.

Storm Prediction Center severe weather database, 1950 to 2025.

Every storm within 100 miles

1. Tropical storms and hurricanes (34 kt or more, still tropical) at closest approach. Post-tropical remnants with gale-force winds are listed but not counted. Direct: track within 50 miles; near: within 100 miles. Distance is measured to the county boundary for counties and to the city centre for cities, using positions interpolated hourly between HURDAT2 fixes.

National Hurricane Center HURDAT2, 1851 to 2025.

Smoke overhead

1. A smoke day is a date on which a smoke plume traced by NOAA Hazard Mapping System analysts from satellite imagery covered this place's point (the county's population centre or the city centre). Counts here are of medium or heavy smoke. Since 2018 analysts have often drawn light smoke as one area over most of the continent, so light-smoke counts are not comparable from year to year. The plumes show smoke anywhere in the air above, not air quality at the ground, and smoke hidden by cloud is missed.

NOAA Hazard Mapping System smoke analysis, 2011 to 2026, retrieved October 30, 2026.

Flood insurance figures are for New London County, the county that contains Groton.

Claims by ZIP code

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026. NOAA Storm Events through 2026.

River crests

River gauges in New London County, the county that contains Groton.

River gauges

1. Crests are the highest and the recent crests the National Weather Service lists for each river gauge in the county that has a flood stage, not every flood. Flood categories use each gauge's current flood stages; crests from before levees, dams or channel changes may not be comparable. Crests measured on an old datum are left out of the rankings.

NOAA National Water Prediction Service gauge records, retrieved October 30, 2026.

High tide flooding

Tide gauges in New London County.

1. High tide flooding days are days on which a NOAA tide gauge recorded water at or above NOAA's minor flood threshold, set from the gauge's tide range, counted by meteorological year (May to April). These are the counts in NOAA's annual high tide flooding reports; they are not National Weather Service flood stages. Years with less than 80 percent of data are left out.

NOAA CO-OPS high tide flooding counts, through April 2026, retrieved October 30, 2026.

The drought index is for New London County, the county that contains Groton.

1. The Palmer Drought Severity Index is computed by NOAA each month from the county's average temperature and precipitation, relative to the county's own climate. Zero is normal; -3 or lower is severe drought and -4 or lower extreme drought. It describes the long-term balance of moisture, not water supply or crop losses.

NOAA NCEI nClimDiv county Palmer Drought Severity Index, 1895 to September 2026, issued October 6, 2026.

1. Earthquakes of magnitude 2.5 or more in the USGS Comprehensive Catalog since 1900. Within 50 miles means the epicentre lies within 50 miles of the city centre.
2. Small earthquakes were under-recorded before the modern seismic networks of the 1970s and are still missed in remote areas, so early decades read low. Magnitudes are as the catalogue reports them and mix scales (moment, local and body-wave).

USGS ANSS Comprehensive Earthquake Catalog, 1900 to present, retrieved October 30, 2026.

Tsunamis

Tsunami records for New London County.

1. Places where NOAA's Global Historical Tsunami Database records a tsunami's water arriving, with the greatest height it reached above sea level at the time. Only tsunamis NOAA rates probable or definite are counted. Heights from eyewitness accounts and tide gauges are mixed, and older events are less completely recorded.

NOAA NCEI/WDS Global Historical Tsunami Database, retrieved October 30, 2026.

Mapped landslides

Landslides mapped in New London County.

Mapped by NASA (1).

1. Landslides mapped in the USGS compilation of landslide inventories across the United States (version 3.0, 2025), rated probable or better. The compilation joins inventories made by federal and state agencies for different purposes and areas, so the number mapped in a county reflects how closely it has been surveyed as much as how often its slopes fail. An area with few records may simply not have been mapped. Deaths are as recorded in the inventories; a slide listed in two inventories is counted once.

USGS Landslide Inventories across the United States, version 3.0, retrieved October 27, 2026.

More event types since 1996

Costliest events since 1996

1. Mar 30, 2010Flood$4.0 million
   National Weather Service narrative

   In Stonington and N. Stonington, numerous roads were closed and reports of numerous houses with serious basement flooding, up to 3 ft. high, was received. The intersection of Montauk Ave. and Mistuxet Ave. just outside of Mystic was also closed due to flooding. Several basement offices in Stonington Town Hall on Elm St. were flooded. Floodwaters also caused extensive damage to the bridge over Shunock Brook on Wyassup Rd. between Avery Ln. and Main St., and a historic 150 year old building that houses the Watermark Cafe and the Village Hardware Store. Lantern Hill Rd, Grindstone Hill Rd., Loin Hill Rd. and Pinewoods Rd. were completely washed out and in need of major repairs.

2. Aug 4, 2020Tropical Storm, Northern New London$1.5 million
   National Weather Service narrative

   Numerous trees and power lines were downed throughout the county. This resulted in numerous power outages. ||Nearby to the northwest corner of the county, Willimantic-Windham Airport reported a maximum sustained wind of 39 mph at 310 pm LST and a peak gust of 52 mph at 352 pm LST.

3. Aug 4, 2020Tropical Storm, Southern New London$1.5 million
   National Weather Service narrative

   Numerous trees and power lines were downed throughout the county. This resulted in numerous power outages. ||Groton-New London Airport reported a maximum sustained wind of 46 mph at 356 pm LST and a peak gust of 58 mph at 437 pm LST. The Stonington Weatherflow site reported a maximum sustained wind of 42 mph and a peak gust of 54 mph at 422 pm LST. The United States Coast Guard Academy reported a peak gust of 52 mph at 324 pm LST.||There were no reports of coastal flooding as the highest storm surge did not coincide with high tide and was during a period of low astronomical tides.

4. Mar 30, 2010Flood$1.1 million
   National Weather Service narrative

   Major flooding occurred on the Quinnebaug River at Jewett City. The river crested at 23.26 ft. at 0630 EST on March 31, 2010 and remained above flood stage until the morning of April 1. As a result, roads were damaged by flood waters including, South Main St. A retaining wall was also damaged on School St. A woman nearly electrocuted herself while attempting to unplug a clothes dryer. Water inside the walls of her 24 Wedgewood Dr. apartment caused the wire to become live and she was badly shocked and taken to the hospital. Coincidentally, 13 other apartments were evacuated after the ceilings collapsed inside the first and second-floor apartments. The Jewett City sewage treatment…

5. Oct 29, 2012High Wind, Northern New London$1.0 million
   National Weather Service narrative

   A wind gust up to 70 mph was reported in Stonington by an emergency manager at 3 pm.

6. Sep 2, 2021Flash Flood$706,000
   National Weather Service narrative

   Heavy rain and flash flooding resulted in uninsured damages of $706,239 across New London County.

7. Mar 30, 2010Flood$500,000
   National Weather Service narrative

   In Old Mystic, raging waters from a small stream that empties into the Mystic River tore out a small bridge on Route 184, flooded numerous homes and businesses, such as the Old Mystic General Store, post office and Old Mystic Mill on Main St., as well as trapped cars. Route 27 nearby remained closed and River Rd. was eventually closed as well.||Total rainfall amounts received across New London County ranged from 6.04 in Old Lyme to 8.60 in Mystic.

8. Oct 29, 2012High Wind, Southern New London$300,000
   National Weather Service narrative

   A wind gust up to 75 mph was reported at Groton Airport at 335 pm. A wind gust up to 70 mph was reported in Stonington by an emergency manager at 3 pm.

9. Mar 29, 2010Flood$260,000
   National Weather Service narrative

   In Groton, many streams were above bankfull and numerous homes experienced basement flooding.

10. Nov 7, 2012High Wind, Southern New London$200,000
    National Weather Service narrative

    A mesonet station measured a 60 mph wind gust at 3 am on November 8th, about 2 miles south of Groton. The ASOS at Groton Airport measured a wind gust of 45 mph at 9:41 pm on November 7th.

1. Storm Events records before 1996 cover only tornadoes, thunderstorm wind and hail. Damage figures are as reported by the National Weather Service at the time, not adjusted for inflation.

NOAA NCEI Storm Events Database, 1950 to 2026, issued October 26, 2026.

All-time high

102°FAug 10, 2001

All-time low

−21°FJan 21, 1994

Warmest night

79°F3 times, most recently Aug 9, 2022

Coldest day

8°FJan 21, 1985

Wettest day

6.34 inSep 2, 2021

Snowiest day

20.0 inFeb 9, 2013

Hottest year

2012mean 54.4°F

Coldest year

1958mean 49.1°F

Wettest year

198367.05 in

Driest year

196526.90 in

Snowiest season

74.3 in1995-96

Station Norwich Public Utility Plt (USC00065910), 20 ft elevation, 13.9 miles from the city centre. Daily records from 1956 to October 28, 2026; 93.7% of days in the last 30 years are complete. Records at a single station can differ from a city’s official threaded record, which may combine several stations.

NOAA NCEI Global Historical Climatology Network Daily.

Declarations for New London County.

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA Disaster Declarations Summaries, retrieved October 30, 2026. Statewide declarations are not listed.

• Tornadoes NOAA Storm Prediction Center severe weather database, through 2025.
• Tropical cyclones NOAA National Hurricane Center HURDAT2 (Atlantic; Northeast and Central Pacific), through 2025.
• Wildfire USGS/USFS Monitoring Trends in Burn Severity, through 2026.
• Storm events NOAA NCEI Storm Events Database, through 2026.
• Flood insurance OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026.
• Declarations OpenFEMA Disaster Declarations Summaries v2, retrieved October 30, 2026.
• Weather records NOAA NCEI Global Historical Climatology Network Daily, station USC00065910.
• River crests NOAA National Weather Service, National Water Prediction Service river gauges, retrieved October 30, 2026.
• Tide gauges NOAA CO-OPS high tide flooding counts, retrieved October 30, 2026.
• Drought NOAA NCEI nClimDiv county Palmer Drought Severity Index, through September 2026.
• Smoke NOAA NESDIS Hazard Mapping System smoke analysis, retrieved October 30, 2026.
• Tsunamis NOAA NCEI/WDS Global Historical Tsunami Database.
• Landslides USGS Landslide Inventories across the United States, version 3.0 (2025).
• Earthquakes USGS ANSS Comprehensive Earthquake Catalog (ComCat), retrieved October 30, 2026.

Joins, thresholds and known limits are set out in the methodology. Found an error? Report it. Page built October 30, 2026.