Marion (IL) Temperature by Month

The average annual maximum temperature in Marion, Illinois, United States of America is 19°C (66°F), with daytime highs ranging from 5°C (41°F) in January to 31°C (88°F) in July. This page covers monthly averages, day-night differences, and how Marion compares to cities worldwide.

In Marion, temperatures can shift dramatically between very warm in summer and cold in winter. Nights follow the same pattern, with lows ranging from 20°C (68°F) in July to -4°C (25°F) in January.

The chart below illustrates the average maximum day and minimum night temperatures in Marion by month:

The coldest point of the day usually falls between 4 AM and 6 AM, with temperatures peaking around 3 PM.

The chart below shows the average temperature throughout the year:

Marion's average annual maximum temperature is 19°C (66°F). To put that in context, here's how it compares to a few well-known destinations:

Seville, Spain averages 23°C (73°F) a year, one of the warmer cities in Western Europe, with long hot summers.

Queenstown, New Zealand averages 10°C (50°F) annually, remember seasons are flipped, so its coldest months fall in June and July.

Boston, USA averages 16°C (61°F) annually, with four distinct seasons and cold winters that rival northern Europe.

Adelaide, Australia averages 21°C (70°F) a year, with warm summers, mild winters, and relatively low rainfall year-round.

Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.

The readings come from a range of sources, land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.

Whether a city sits on the coast or deep inland makes a significant difference to its climate. Coastal areas tend to have more stable temperatures year-round, large bodies of water absorb heat slowly in summer and release it gradually in winter, keeping extremes in check. Cities far from the sea don't benefit from that buffer, which is why continental climates tend to have hotter summers and colder winters than their coastal counterparts at the same latitude.

For more on Marion's weather, including monthly rainfall, sunshine hours, and humidity, visit our Marion climate page.