Illinois weather in August 2025

Q: How hot is it in Illinois in August?

Daytime temperatures usually reach 28°C in Chicago, Illinois in August with moderate heat and humidity, falling to 16°C at night.

Q: How sunny is it in Illinois in August?

There are normally 9 hours of bright sunshine each day in Chicago, Illinois in August - that's 67% of daylight hours.

Q: How warm is the sea around Illinois in August?

The average sea temperature around Chicago, Illinois in August is 21°C.

Q: Does it rain in Illinois in August?

There are usually 9 days with some rain in Chicago, Illinois in August and the average monthly rainfall is 97mm.

Expect 28°C daytime maximum temperatures in the shade with on average 9 hours of sunshine per day in Illinois in August. Check more long-term weather averages for Illinois in August before you book your next holiday to Illinois in 2025/2026.

28
28°C max day temperature
9
9 hours of sunshine per day
9
9 days with some rainfall
16
16°C min night temperature
14
14 hours of daylight per day
M
Moderate heat & humidity
97
97 mm of monthly rainfall
8
8 (Very High) UV index
21
21°C sea temperature

More about Illinois

Illinois by month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Recommended for Illinois

Virgin Holidays: Latest offers on 2024 holidays

Sale

Book online & save on long haul holidays in 2024
Destinations include New York, Caribbean & beyond
Ideal for summer, winter & half term family holidays

Go to Virgin Holidays deal >>

View all Virgin Holidays offers

The August weather guide for Illinois (Chicago) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Top Illinois destinations

Below are average maximum temperatures at popular countries, regions and places in Illinois in August. Select a holiday destination to see more weather parameters.

29
Springfield
28
Chicago

All Illinois destinations

Metric (°C / mm) | Imperial (°F / inches)

More about the USA

How hot is it in Illinois in August?

Daytime temperatures usually reach 28°C in Chicago, Illinois in August with moderate heat and humidity, falling to 16°C at night.

How sunny is it in Illinois in August?

There are normally 9 hours of bright sunshine each day in Chicago, Illinois in August - that's 67% of daylight hours.

How warm is the sea around Illinois in August?

The average sea temperature around Chicago, Illinois in August is 21°C.

Does it rain in Illinois in August?

There are usually 9 days with some rain in Chicago, Illinois in August and the average monthly rainfall is 97mm.

Illinois August sunrise & sunset times

Browse the sunrise and sunset times for Illinois in August 2025. Select a month to view Illinois sunrise and sunset times for the next 12 months. The Illinois sunrise and sunset times shown below are for Chicago.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Date	Sunrise times	Sunset times
Friday, 1st August 2025	04:45	19:08
Saturday, 16th August 2025	05:00	18:49
Sunday, 31st August 2025	05:16	18:25

Be inspired

Get your weekly fix of holiday inspiration from some of the world's best travel writers plus save on your next trip with the latest exclusive offers

We promise not to share your details

Popular travel offers

Illinois - quick facts
Flight time^✝	8.5 hours
Time difference	UK -6 hours
Language(s)	English
Currency	US Dollar
Electricity	A + B plug (120V)
Driving side	Right
Visa^✝	Yes
Why visit?	Culture
Tourist info	Illinois Department of Commerce & Economic Opportunity