Old Mystic has chilly winters and pleasant summers
A typical July afternoon reaches 82°, a January night drops to 22°, and about 25 inches of snow falls in a normal winter.
A year in Old Mystic at a glance
Each month’s typical high and low, and what it brings.
What stands out about Old Mystic’s climate
Read from where Old Mystic sits among Connecticut’s towns. The page puts what stands out first.
25 inches of snow, 46 of rain and melt
October is the wettest month and February the driest. Rain or snow falls on about 128 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Living with Old Mystic’s climate
What the numbers mean for a garden, a driveway, a furnace and a free afternoon.
207 frost-free days. The last frost comes by Apr 8 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 2.
About 25" a winter over 8 days with an inch or more, most in February. Snow covers the ground about 21 days a year.
Months averaging under 55° run from October through April. Heating is 88% of the year’s heating-and-cooling load.
About 3 days a year reach 90°, and July afternoons average 82°.
The nicest months are May, June, July, August, September and October. 0.4 miles of trails are waiting.
Parks & trails →Normals are averages. Ice storms, nor’easters, floods and heat waves are on the natural hazards page.
Natural hazards →What a year in Old Mystic feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
Warmer than it used to be
The last 30 years in Old Mystic averaged 2.1° warmer than the 1900s. The biggest change is in December (+3.7°).
A bigger shift than in 96% of U.S. towns.
Change by month
About 207 frost-free days a year
In half of years the last 32° night comes by April 8 and the first by November 2.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
Old Mystic and its neighbors
Ledyard has the coldest January nights next door (21°) and Ledyard the hottest July afternoons (82°). Tap a town to see its climate.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
How Old Mystic compares
Against every U.S. town on TownTapestry, each counted once, with its place in Connecticut.
Old Mystic 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 | 39° | 22° | 3.5" | 5.8" | 11 | 7 | 22° – 37° |
| February | 40° | 23° | 3.0" | 8.3" | 10 | 7 | 20° – 38° |
| March | 47° | 30° | 4.4" | 3.9" | 12 | 3 | 33° – 46° |
| April | 58° | 38° | 4.1" | 0.8" | 12 | 0 | 44° – 52° |
| May | 67° | 48° | 3.6" | 0 | 12 | 0 | 53° – 62° |
| June | 76° | 57° | 3.8" | 0 | 10 | 0 | 64° – 69° |
| July | 82° | 64° | 3.2" | 0 | 10 | 0 | 69° – 77° |
| August | 81° | 62° | 3.7" | 0 | 9 | 0 | 68° – 76° |
| September | 74° | 55° | 4.1" | 0 | 10 | 0 | 62° – 68° |
| October | 63° | 45° | 4.5" | 0 | 10 | 0 | 51° – 60° |
| November | 53° | 36° | 3.7" | 0.5" | 10 | 0 | 40° – 48° |
| December | 44° | 28° | 4.4" | 5.2" | 12 | 4 | 29° – 47° |
| Year | 60° | 42° | 45.9" | 24.5" | 128 | 21 |
Heating and cooling a home in Old Mystic
88% of the work is heating, so the furnace matters far more than the air conditioner.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. Source: NOAA station normals.
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 20° to 38°. June is the most reliable, staying within 5°.
Common questions about Old Mystic’s climate
What is the coldest month in Old Mystic?
January, with a typical high of 39° and a low of 22°.
What is the hottest month in Old Mystic?
July, with a typical high of 82° and a low of 64°. About 3 days a year reach 90°.
How much snow does Old Mystic get?
About 25 inches in a normal winter, most of it in February.
When is the first frost in Old Mystic?
In half of years the first 32° night comes by November 2, and the last spring frost by April 8.
What is the rainiest month in Old Mystic?
October, with 4.5 inches of rain and melted snow. The year totals 46 inches.
Neighbors talk weather
Gardens, snow, and the best days of the year in Old Mystic.
Your answer becomes a post in Town Square.
Temperatures and rainfall come from NOAA’s gridded climate normals for Old Mystic itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Groton, CT (4 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000. Today’s forecast: National Weather Service.