Dennis, MA climate
Dennis has chilly winters and pleasant summers. A typical July afternoon reaches 79°, a January night drops to 24°, and about 22 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Dennis feels like
Winter
Spring
Summer
Fall
Dennis 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° | 24° | 3.9" | 9.5" | 10 | 5 | 23° – 38° |
| February | 40° | 25° | 3.3" | 6.3" | 10 | 7 | 23° – 38° |
| March | 45° | 30° | 4.4" | 3.6" | 10 | 3 | 32° – 43° |
| April | 54° | 38° | 4.1" | 0 | 11 | 0 | 42° – 49° |
| May | 63° | 47° | 3.2" | 0 | 10 | 0 | 50° – 59° |
| June | 72° | 56° | 3.3" | 0 | 9 | 0 | 60° – 68° |
| July | 79° | 63° | 2.5" | 0 | 7 | 0 | 67° – 75° |
| August | 78° | 62° | 3.4" | 0 | 8 | 0 | 67° – 74° |
| September | 72° | 56° | 3.8" | 0 | 8 | 0 | 61° – 67° |
| October | 62° | 46° | 4.4" | 0 | 10 | 0 | 51° – 60° |
| November | 53° | 38° | 4.0" | 0 | 10 | 0 | 41° – 49° |
| December | 44° | 30° | 4.7" | 2.1" | 12 | 2 | 31° – 46° |
| Year | 58° | 43° | 45.0" | 21.5" | 113 | 16 |
“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 Dennis
Dennis gets 45 inches of rain and melted snow a year. December is the wettest month and July the driest. Rain or snow falls on about 113 days a year. Snow covers the ground about 16 days of the year.
About 204 frost-free days a year
In half of years the last 32° night comes by April 13 and the first one by November 3. That leaves about 204 frost-free days for gardens, longer than 75% of U.S. towns.
Heating and cooling a home in Dennis
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Dennis, 93% of that work is heating and 7% 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.
Dennis and its neighbors
Dennis borders 3 towns with climate data. January nights across them vary by 1.1°. Brewster has the coldest January nights (24°) and Yarmouth the hottest July afternoons (79°). Dennis’s January low is 24° and its July high 79°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Dennis 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 Dennis averaged 2.0° warmer than the 1900s. The biggest change is in December (+3.5°). The shift is larger than in 95% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Dennis’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. January swings the most: between 1991 and 2020 its average temperature ranged from 23° to 38°. September is the most reliable, staying within 7°.
Common questions about Dennis’s climate
What is the coldest month in Dennis?
January, with a typical high of 39° and a low of 24°.
What is the hottest month in Dennis?
July, with a typical high of 79° and a low of 63°.
How much snow does Dennis get?
About 22 inches in a normal winter, most of it in January.
When is the first frost in Dennis?
In half of years the first 32° night comes by November 3, and the last spring frost by April 13.
What is the rainiest month in Dennis?
December, with 4.7 inches of rain and melted snow. The year totals 45 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Dennis itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Hyannis, MA (8 mi, snow) and West Harwich, MA (4 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.