Lake Forest, IL climate
Lake Forest has chilly, snowy winters and pleasant summers. A typical July afternoon reaches 82°, a January night drops to 17°, and about 34 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Lake Forest feels like
Winter
Spring
Summer
Fall
Lake Forest 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 | 31° | 17° | 1.9" | 11.3" | 11 | 20 | 15° – 35° |
| February | 35° | 20° | 1.8" | 7.7" | 9 | 14 | 15° – 38° |
| March | 45° | 29° | 2.2" | 5.6" | 10 | 7 | 29° – 52° |
| April | 56° | 38° | 3.8" | 1.1" | 13 | 1 | 39° – 53° |
| May | 67° | 48° | 4.3" | 0 | 13 | 0 | 52° – 64° |
| June | 77° | 58° | 4.4" | 0 | 12 | 0 | 63° – 73° |
| July | 82° | 64° | 3.7" | 0 | 10 | 0 | 68° – 80° |
| August | 81° | 63° | 3.8" | 0 | 10 | 0 | 66° – 77° |
| September | 74° | 56° | 3.4" | 0 | 10 | 0 | 59° – 69° |
| October | 61° | 44° | 3.3" | 0.1" | 11 | 0 | 48° – 59° |
| November | 48° | 33° | 2.5" | 1.9" | 10 | 2 | 32° – 49° |
| December | 36° | 23° | 2.0" | 5.9" | 11 | 10 | 17° – 39° |
| Year | 58° | 41° | 37.1" | 33.6" | 130 | 53 |
“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 Lake Forest
Lake Forest gets 37 inches of rain and melted snow a year. June is the wettest month and February the driest. Rain or snow falls on about 130 days a year. Snow covers the ground about 53 days of the year.
About 176 frost-free days a year
In half of years the last 32° night comes by April 26 and the first one by October 21. That leaves about 176 frost-free days for gardens, shorter than 53% of U.S. towns.
Heating and cooling a home in Lake Forest
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Lake Forest, 89% of that work is heating and 11% 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.
Lake Forest and its neighbors
Lake Forest borders 8 towns with climate data. January nights across them vary by 1.7°. Mettawa has the coldest January nights (16°) and Lincolnshire the hottest July afternoons (83°). Lake Forest’s January low is 17° and its July high 82°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Lake Forest 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 Lake Forest averaged 1.2° warmer than the 1900s. The biggest change is in December (+2.5°). The shift is smaller than in 51% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Lake Forest’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 15° to 38°. June is the most reliable, staying within 10°.
Common questions about Lake Forest’s climate
What is the coldest month in Lake Forest?
January, with a typical high of 31° and a low of 17°.
What is the hottest month in Lake Forest?
July, with a typical high of 82° and a low of 64°. About 17 days a year reach 90°.
How much snow does Lake Forest get?
About 34 inches in a normal winter, most of it in January.
When is the first frost in Lake Forest?
In half of years the first 32° night comes by October 21, and the last spring frost by April 26.
What is the rainiest month in Lake Forest?
June, with 4.4 inches of rain and melted snow. The year totals 37 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Lake Forest itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Chicago Botanic Garden, IL (8 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.