Ottawa, IL Weather & Climate Normals
What a normal year in Ottawa actually looks like
On the 30-year record NOAA keeps for Ottawa, IL, the comfort score comes out to 45/100, strongly seasonal: Comfortable weather is limited to a shorter window; summers, winters, or precipitation swing wide. Only 5 months a year land in the 55–75°F range this site treats as mild.
How much Ottawa's weather actually swings
Average temperatures in Ottawa run from 23°F in Jan up to 73°F in Jul, a 50.2°F seasonal swing, one of the widest gaps in this dataset.
Ottawa, month by month
| Month | Avg high | Avg low | Precip | Snow |
|---|---|---|---|---|
| Jan | 31°F | 14°F | 1.95in | 8.4in |
| Feb | 35°F | 17°F | 1.9in | 7.3in |
| Mar | 48°F | 27°F | 2.54in | 2.9in |
| Apr | 61°F | 37°F | 3.59in | 0.3in |
| May | 73°F | 49°F | 4.7in | 0in |
| Jun | 81°F | 58°F | 4.92in | 0in |
| Jul | 84°F | 62°F | 3.85in | 0in |
| Aug | 82°F | 61°F | 4.09in | 0in |
| Sep | 77°F | 53°F | 3.46in | 0in |
| Oct | 64°F | 41°F | 3.2in | 0in |
| Nov | 49°F | 30°F | 2.72in | 0.8in |
| Dec | 37°F | 21°F | 2.11in | 5.3in |
If you're timing a visit, May, Jun, Jul, Aug, and Sep are Ottawa's mildest stretch; if you're moving there, you should plan around Jan's cold instead.
How wet Ottawa actually gets
Over a typical year, Ottawa sees about 39.03in of precipitation a year across roughly 124 days with measurable rain or snow, with 25in of snow a year.
Ottawa against the rest of the country
Out of 4876 cities scored here, Ottawa comes in at 3358; within IL alone it ranks 135 of 330. Population is about 18,775.
Checking the actual forecast
These figures come from Marseilles Lock, IL US, the NOAA station 4.0 miles from Ottawa, averaged over 30 years, not tomorrow's forecast.
More on how this is worked out
Why some cities show no snow or rain figure · What a 30-year climate normal actually is