Warm
Average highs sit around 29°C, giving warm days by monthly-average standards.
Weather Guide
Ottawa, Illinois, United States Average Monthly Weather
Weather score50Mixed annual avg
Best months: July, August, June
Across the year, average daytime temperatures are around 16°C, sunshine averages 6.8h per day, and rainfall totals about 860mm.
Annual weather
Annual averages
Temp
16°C
Rain
860mm
Annual total
Sun
6.8h
Weather score
50
Mixed avg
Seasonal climate calendar
TemperatureTemp
RainRain
SunSun
Weather scoreWeather score
Trip feel
Showers
Rainfall averages 90mm, so some wet days are possible.
Bright
Sunshine averages 9h per day, so bright days are a strong part of the month.
Map
Weather map
Compare Ottawa, Illinois, United States with nearby places by weather score, rain, sun, temperature, and swim conditions.
Temperature
August29°C average high
August is one of Ottawa's warmest months, with daytime heat above the yearly average.
Warmest monthsMay to September
This stretch sets the upper range for average daytime heat.
Rain
August90mm average rain
August is wetter than Ottawa's yearly average, so flexible plans matter more.
Driest monthsJanuary to February, October, and December
This is the drier part of the year, when outdoor plans usually need less weather flexibility.
Sun
August9 hours average sun
August is brighter than Ottawa's yearly average, though the strongest sunshine usually sits closer to the peak months.
Brightest monthsMay to August
This stretch has the strongest sunshine in the monthly averages.
Weather score
August78 weather score
August scores above Ottawa's yearly average, so the overall weather mix is stronger than most months.
Best weather monthsJune to August
These months have the strongest weather score in the monthly averages.
