Climate in Illinois

Most of Illinois has a humid continental climate, with hot, humid summers and cold winters.The southernmost part of the state borders on a humid subtropical climate, with milder winters. The weather in Illinois can be fairly extreme. In summer (June to August) temperatures rise to between 80ºF (27ºC) and 90ºF (32°C) and there's high humidity, while in winter (January to March) it can be wet and cold, with temperatures as low as 12ºF (-11ºC) and icy winds whipping off Lake Michigan. Snow is likely in winter. May and September are the most pleasant months, with reliably warm, sunny days.