San Jose, IL climate
San Jose has chilly winters and warm summers. A typical July afternoon reaches 86°, a January night drops to 18°, and about 13 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in San Jose feels like
Winter
Spring
Summer
Fall
San Jose 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 | 34° | 18° | 2.1" | 5.5" | 8 | 10 | 19° – 38° |
| February | 39° | 22° | 1.9" | 2.8" | 7 | 3 | 18° – 41° |
| March | 51° | 31° | 2.6" | 1.7" | 8 | 1 | 34° – 55° |
| April | 65° | 41° | 4.0" | 0 | 11 | 0 | 45° – 59° |
| May | 75° | 53° | 4.6" | 0 | 11 | 0 | 58° – 72° |
| June | 83° | 62° | 4.3" | 0 | 10 | 0 | 68° – 75° |
| July | 86° | 65° | 4.2" | 0 | 9 | 0 | 70° – 81° |
| August | 85° | 62° | 3.5" | 0 | 8 | 0 | 68° – 79° |
| September | 79° | 55° | 3.3" | 0 | 7 | 0 | 61° – 72° |
| October | 66° | 43° | 3.3" | 0 | 9 | 0 | 50° – 60° |
| November | 51° | 32° | 2.7" | 0.3" | 7 | 0 | 34° – 50° |
| December | 39° | 23° | 2.1" | 2.6" | 6 | 4 | 17° – 41° |
| Year | 63° | 42° | 38.5" | 12.9" | 99 | 19 |
“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 San Jose
San Jose gets 38 inches of rain and melted snow a year. May is the wettest month and February the driest. Rain or snow falls on about 99 days a year. Snow covers the ground about 19 days of the year.
About 182 frost-free days a year
In half of years the last 32° night comes by April 17 and the first one by October 18. That leaves about 182 frost-free days for gardens, longer than 55% of U.S. towns.
Heating and cooling a home in San Jose
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In San Jose, 85% of that work is heating and 15% 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.
How San Jose 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 San Jose averaged 1.0° warmer than the 1900s. The biggest change is in December (+2.2°). The shift is smaller than in 71% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at San Jose’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 17° to 41°. June is the most reliable, staying within 8°.
Common questions about San Jose’s climate
What is the coldest month in San Jose?
January, with a typical high of 34° and a low of 18°.
What is the hottest month in San Jose?
July, with a typical high of 86° and a low of 65°. About 27 days a year reach 90°.
How much snow does San Jose get?
About 13 inches in a normal winter, most of it in January.
When is the first frost in San Jose?
In half of years the first 32° night comes by October 18, and the last spring frost by April 17.
What is the rainiest month in San Jose?
May, with 4.6 inches of rain and melted snow. The year totals 38 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for San Jose itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Mason City 4se, IL (10 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.