Dorchester, IL climate
Dorchester has chilly winters and warm summers. A typical July afternoon reaches 87°, a January night drops to 21°, and about 14 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Dorchester feels like
Winter
Spring
Summer
Fall
Dorchester 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 | 30-yr range |
|---|---|---|---|---|---|---|
| January | 37° | 21° | 2.5" | 5.7" | 6 | 23° – 41° |
| February | 43° | 25° | 2.2" | 2.8" | 6 | 22° – 44° |
| March | 53° | 34° | 3.2" | 1.6" | 8 | 36° – 57° |
| April | 66° | 44° | 4.7" | 0.1" | 9 | 47° – 60° |
| May | 75° | 54° | 5.0" | 0 | 10 | 60° – 72° |
| June | 84° | 64° | 4.4" | 0 | 8 | 68° – 77° |
| July | 87° | 67° | 4.1" | 0 | 7 | 71° – 84° |
| August | 86° | 64° | 3.4" | 0 | 6 | 69° – 81° |
| September | 80° | 56° | 3.3" | 0 | 5 | 63° – 73° |
| October | 68° | 45° | 3.3" | 0.1" | 6 | 51° – 63° |
| November | 53° | 35° | 3.4" | 0.7" | 7 | 36° – 52° |
| December | 42° | 26° | 2.5" | 2.9" | 6 | 20° – 43° |
| Year | 64° | 45° | 41.8" | 13.9" | 83 |
“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 Dorchester
Dorchester gets 42 inches of rain and melted snow a year. May is the wettest month and February the driest. Rain or snow falls on about 83 days a year.
About 214 frost-free days a year
In half of years the last 32° night comes by April 4 and the first one by November 5. That leaves about 214 frost-free days for gardens, longer than 80% of U.S. towns.
Heating and cooling a home in Dorchester
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Dorchester, 77% of that work is heating and 23% is cooling.
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.
Dorchester and its neighbors
Dorchester borders 4 towns with climate data. January nights across them vary by 0.8°. Gillespie has the coldest January nights (21°) and Bunker Hill the hottest July afternoons (87°). Dorchester’s January low is 21° and its July high 87°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Dorchester 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 Dorchester averaged 0.8° warmer than the 1900s. The biggest change is in December (+2.0°). The shift is smaller than in 82% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Dorchester’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. December swings the most: between 1991 and 2020 its average temperature ranged from 20° to 43°. June is the most reliable, staying within 9°.
Common questions about Dorchester’s climate
What is the coldest month in Dorchester?
January, with a typical high of 37° and a low of 21°.
What is the hottest month in Dorchester?
July, with a typical high of 87° and a low of 67°. About 29 days a year reach 90°.
How much snow does Dorchester get?
About 14 inches in a normal winter, most of it in January.
When is the first frost in Dorchester?
In half of years the first 32° night comes by November 5, and the last spring frost by April 4.
What is the rainiest month in Dorchester?
May, with 5.0 inches of rain and melted snow. The year totals 42 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Dorchester itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Mt Olive 1 E, IL (9 mi, snow) and Alton - Melvin Price L&d, IL (20 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.