In Illinois, summers bring warm, humid, and wet conditions, while winters are characterized by freezing temperatures, snowfall, and windy weather. Partly cloudy skies are common throughout the year. Temperatures typically range from 20°F to 86°F, with rare occurrences below 2°F or above 95°F.
According to the tourism score, the optimal time for warm-weather activities in Illinois is from early June to mid-September.
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In Illinois, temperatures vary significantly between seasons. The hot season spans approximately 3.8 months, from May 25 to September 19, with daily high temperatures averaging above 76°F. July typically registers as the hottest month, with an average high of 86°F and a low of 68°F.
Conversely, the cold season lasts about 3.0 months, from November 28 to February 29, featuring daily high temperatures below 45°F. January is considered the coldest month in Illinois, with an average low of 21°F and a high of 35°F.
To illustrate fluctuations within each month, rather than solely focusing on monthly totals, we present the rainfall accumulated over a sliding 31-day period centered around each day of the year. Illinois undergoes significant seasonal variations in monthly rainfall.
Rain is prevalent throughout the year in Illinois. May typically sees the highest rainfall, with an average of 4.1 inches.
Conversely, January experiences the least rainfall in Illinois, with an average of 0.8 inches.
Similar to rainfall, we analyze snowfall accumulated over a sliding 31-day period centered around each day of the year to capture variations within months. Illinois experiences some seasonal differences in monthly snowfall.
The snowy season extends for approximately 4.2 months, from November 16 to March 22, with a sliding 31-day snowfall of at least 1.0 inches. January typically records the highest snowfall in Illinois, averaging 3.6 inches.
Conversely, the snow-free period lasts for about 7.8 months, from March 22 to November 16. The least snowfall occurs around July 27, with an average total accumulation of 0.0 inches.
