Mild
Average highs are around 23°C, so days are mild rather than hot.
September verdict
Mixed for holiday weather
Average highs are around 23°C, so days are mild rather than hot. Sunshine averages 7.2h per day, enough for a balanced month. Rainfall averages 90mm, so some wet days are possible.

Monthly averages
Temp
23°C
Rain
90mm
Sun
7.2h
Sea
19°C
Weather score
53
Mixed
Mild
Average highs are around 23°C, so days are mild rather than hot.
Showers
Rainfall averages 90mm, so some wet days are possible.
Some sun
Sunshine averages 7.2h per day, enough for a balanced month.
Cool sea
Sea temperatures average 19°C, so the water can feel cool.
Map
Compare Waukegan, Illinois, United States with nearby places by weather score, rain, sun, temperature, and swim conditions.
September23°C average high
September sits in the warmer part of the year, so midday sightseeing can feel heavier than in cooler months.
Warmest monthsJune to September
This stretch sets the upper range for average daytime heat.
September90mm average rain
September is wetter than Waukegan'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.
September7.2 hours average sun
September sits close to Waukegan's yearly sunshine average, so it is a middle-of-the-pack month for bright days.
Brightest monthsMay to August
This stretch has the strongest sunshine in the monthly averages.
September19°C average sea
September sits in the warmer sea-temperature season, usually making swimming easier to enjoy.
Warmest seaJuly to September
Sea temperatures are usually near 20°C in this stretch, so swimming comfort is at its strongest.
September53 weather score
September sits close to Waukegan's yearly weather-score average, giving a typical overall read on the month.
Best weather monthsJuly to August
These months have the strongest weather score in the monthly averages.