Decatur Weather Forecast

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Last Updated: January 6, 2026

Decatur, Illinois is a city located in the central part of the state with a population of approximately 74,710 residents.


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Summary

Decatur has a humid continental climate with hot summers and cold winters. The city is located near the Sangamon River, which is a major tributary of the Illinois River. The Sangamon River is known to contain high levels of nitrogen and phosphorus due to agricultural practices in the surrounding areas. Outdoor recreation opportunities in Decatur include hiking and biking trails, fishing and boating on area lakes and rivers, and golfing at one of the many local courses. The city also has several parks and nature preserves for residents to enjoy.

       

Weather Forecast

Decatur receives approximately 1000mm of rain per year, with humidity levels near 84% and air temperatures averaging around 12°C. Decatur has a plant hardyness factor of 5, meaning plants and agriculture in this region thrive during a short period during spring and early summer. Most plants will die off during the colder winter months.

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