Cornwall, CT climate
Cornwall has cold, snowy winters and pleasant summers, with plenty of rain. A typical July afternoon reaches 81°, a January night drops to 15°, and about 75 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Cornwall feels like
Winter
Spring
Summer
Fall
Cornwall weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 33° | 15° | 3.5" | 17.8" | 13 | 25 | 15° – 31° |
| February | 36° | 16° | 3.0" | 17.5" | 12 | 25 | 13° – 33° |
| March | 44° | 24° | 3.9" | 14.9" | 12 | 22 | 26° – 44° |
| April | 57° | 34° | 3.7" | 3.9" | 13 | 5 | 40° – 50° |
| May | 68° | 44° | 4.0" | 0 | 14 | 0 | 51° – 62° |
| June | 76° | 54° | 4.7" | 0 | 13 | 0 | 62° – 68° |
| July | 81° | 59° | 4.7" | 0 | 12 | 0 | 65° – 74° |
| August | 79° | 57° | 4.6" | 0 | 11 | 0 | 64° – 71° |
| September | 72° | 50° | 4.9" | 0 | 10 | 0 | 57° – 66° |
| October | 60° | 39° | 4.8" | 1.4" | 12 | 0 | 45° – 55° |
| November | 48° | 30° | 3.7" | 4.4" | 11 | 4 | 34° – 44° |
| December | 37° | 21° | 4.3" | 15.0" | 14 | 19 | 22° – 41° |
| Year | 57° | 37° | 49.7" | 74.9" | 148 | 98 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Cornwall
Cornwall gets 50 inches of rain and melted snow a year. September is the wettest month and February the driest. Rain or snow falls on about 148 days a year. Snow covers the ground about 98 days of the year.
About 161 frost-free days a year
In half of years the last 32° night comes by May 3 and the first one by October 11. That leaves about 161 frost-free days for gardens, shorter than 70% of U.S. towns.
Heating and cooling a home in Cornwall
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Cornwall, 95% of that work is heating and 5% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Cornwall and its neighbors
Cornwall borders 5 towns with climate data. January nights across them vary by 0.9°. Goshen has the coldest January nights (14°) and Canaan the hottest July afternoons (82°). Cornwall’s January low is 15° and its July high 81°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Cornwall compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Cornwall averaged 1.8° warmer than the 1900s. The biggest change is in December (+3.3°). The shift is larger than in 89% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Cornwall’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. February swings the most: between 1991 and 2020 its average temperature ranged from 13° to 33°. June is the most reliable, staying within 6°.
Common questions about Cornwall’s climate
What is the coldest month in Cornwall?
January, with a typical high of 33° and a low of 15°.
What is the hottest month in Cornwall?
July, with a typical high of 81° and a low of 59°. About 1 days a year reach 90°.
How much snow does Cornwall get?
About 75 inches in a normal winter, most of it in January.
When is the first frost in Cornwall?
In half of years the first 32° night comes by October 11, and the last spring frost by May 3.
What is the rainiest month in Cornwall?
September, with 4.9 inches of rain and melted snow. The year totals 50 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Cornwall itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Norfolk 2 Sw, CT (10 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.