Waterloo, IL climate
Waterloo has chilly winters and warm summers. A typical July afternoon reaches 88°, a January night drops to 24°, and about 9 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Waterloo feels like
Winter
Spring
Summer
Fall
Waterloo 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 | 40° | 24° | 2.6" | 2.8" | 8 | 26° – 42° |
| February | 46° | 28° | 2.3" | 3.1" | 6 | 27° – 47° |
| March | 56° | 36° | 3.6" | 0.7" | 9 | 39° – 60° |
| April | 68° | 45° | 5.0" | 0.3" | 11 | 50° – 62° |
| May | 76° | 56° | 5.0" | 0 | 12 | 61° – 74° |
| June | 85° | 65° | 4.4" | 0 | 9 | 70° – 79° |
| July | 88° | 68° | 4.0" | 0 | 8 | 74° – 85° |
| August | 87° | 66° | 3.4" | 0 | 7 | 71° – 83° |
| September | 80° | 59° | 3.4" | 0 | 6 | 65° – 76° |
| October | 69° | 47° | 3.2" | 0 | 8 | 53° – 64° |
| November | 55° | 36° | 3.5" | 0.4" | 9 | 38° – 53° |
| December | 44° | 28° | 2.8" | 1.5" | 8 | 22° – 44° |
| Year | 66° | 46° | 43.1" | 8.8" | 99 |
“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 Waterloo
Waterloo gets 43 inches of rain and melted snow a year. April is the wettest month and February the driest. Rain or snow falls on about 99 days a year.
About 197 frost-free days a year
In half of years the last 32° night comes by April 9 and the first one by October 26. That leaves about 197 frost-free days for gardens, longer than 70% of U.S. towns.
Heating and cooling a home in Waterloo
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Waterloo, 78% of that work is heating and 22% 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.
How Waterloo 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 Waterloo averaged 1.2° warmer than the 1900s. The biggest change is in December (+2.2°). The shift is smaller than in 56% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Waterloo’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 22° to 44°. June is the most reliable, staying within 9°.
Common questions about Waterloo’s climate
What is the coldest month in Waterloo?
January, with a typical high of 40° and a low of 24°.
What is the hottest month in Waterloo?
July, with a typical high of 88° and a low of 68°. About 38 days a year reach 90°.
How much snow does Waterloo get?
About 9 inches in a normal winter, most of it in February.
When is the first frost in Waterloo?
In half of years the first 32° night comes by October 26, and the last spring frost by April 9.
What is the rainiest month in Waterloo?
April, with 5.0 inches of rain and melted snow. The year totals 43 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Waterloo itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Waterloo, IL (2 mi, snow) and Festus, MO (15 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.