Weather in Chicago in August

A good month. August works. It is not the peak, but nothing about it fights you. Highs average 25.1 °C, lows 20 °C, and rain falls on 13 days — nothing in the month is working against you.

August ranks 4 of 12 in Chicago: past the worst of the year but short of September, which is the month to book if the dates are open.

Rain on 13 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: the day barely swings — 5 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest August day reached 32.4 °C and the coldest night fell to 13 °C, and the wettest single day dropped 59 mm — roughly 56% of the month's rain in one day.

August is moderately variable: 50 mm in the driest year against 278 mm in the wettest, around an average of 105 mm. Roughly two Augusts in three land near that average, and the third does something else entirely.

Wind is light at 12 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 77%, high enough to notice on the warm days without dominating them.

How August sits in the year

Temperatures hold steady either side: 25.1 °C in July, 25.1 here, 21.9 in September. Nothing about the timing within the month matters much.

Daylight in August

13.9 hours of daylight, losing 1.2 hours across the month. That is between Chicago's extremes of 15.2 and 9.2 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 30.2 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

August in Chicago versus nearby

If Chicago is one option among several, the nearby comparison is worth making. Milwaukee is close enough to be a coin toss — 2.4 °C warmer, 1 day less rain. Grand Rapids is close enough to be a coin toss — within a degree on temperature, 1 day less rain.

So: August is effectively as good as it gets here — 6 points behind September, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Chicago

See all twelve months in Chicago, or where else to go in August.