Illinois weather in May 2025

Expect 21°C daytime maximum temperatures in the shade with on average 9 hours of sunshine per day in Illinois in May. Check more long-term weather averages for Illinois in May before you book your next holiday to Illinois in 2025/2026.

  • 21°C maximum daytime temperature in May in Illinois (Chicago)21
    21°C max day temperature
  • 9 hours of sunshine per day
  • 11 days with some rainfall in May in Illinois (Chicago)11
    11 days with some rainfall
  • 9°C minimum night-time temperature in May in Illinois (Chicago)9
    9°C min night temperature
  • 15 hours of daylight per day in May in Illinois (Chicago)15
    15 hours of daylight per day
  • No heat & humidity in May in Illinois (Chicago)0
    No heat & humidity
  • 84 mm monthly rainfall in May in Illinois (Chicago)84
    84 mm of monthly rainfall
  • UV (maximum) index 7 (High) in May in Illinois (Chicago)7
    7 (High) UV index
  • 6°C sea temperature in May in Illinois (Chicago)6
    6°C sea temperature

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The May 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 May. Select a holiday destination to see more weather parameters.

All Illinois destinations

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

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More about the USA

How hot is it in Illinois in May?

Daytime temperatures usually reach 21°C in Chicago, Illinois in May, falling to 9°C at night.

How sunny is it in Illinois in May?

There are normally 9 hours of bright sunshine each day in Chicago, Illinois in May - that's 62% of daylight hours.

Is the sea cold around Illinois in May?

The average sea temperature around Chicago, Illinois in May is 6°C.

Does it rain in Illinois in May?

There are usually 11 days with some rain in Chicago, Illinois in May and the average monthly rainfall is 84mm.

Illinois May sunrise & sunset times

Browse the sunrise and sunset times for Illinois in May 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.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Thursday, 1st May 2025 04:46 18:50
Friday, 16th May 2025 04:29 19:05
Saturday, 31st May 2025 04:18 19:19

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