The typical weather of Illinois consists of the standard climatic environment that has been often observed in the state of Illinois during the past. Due to its approximately 400 miles (640 km) extent and central location in the continent, Illinois has an extensively unstable weather conditions. The major parts of Illinois have a moist continental climate condition along with scorching, dry and moist summer season and moderately cool to extremely cold winter season. The extreme south parts of the Illinois, from approximately Carbondale towards south, generally faces a moist subtropical weather condition together with more modest winter seasons. Normal rainfall in a year for Illinois ranges from approximately over 48 inches (or 1,200 mm) at the extreme south edge to 35 inches (or 890 mm) in the north most part of the state. Standard yearly snow goes beyond 38 inches (or 970 mm) in Chicago, whereas the southern part of the state in general gets less than 14 inches (or 360 mm). The maximum temperature ever observed in Illinois was 117 °F (47 °C), and was noted on July 14, 1954, at East St. Louis, whereas the lower most temperature was -37 °F (or -39 °C), observed on January 15, 2009, at Rochelle.
Illinois is subjected to the thunderstorm for an average of a 50 day period in a year which places it, to some extent, over the standard for number of thunderstorm days for the entire United States. Illinois suffers the torments of heavy cyclones with a standard of 35 cyclones happening every twelve months, which positions a great part of the state at approximately 5 cyclones per 10,000 square miles (or 30,000 km2) per annum. The most devastating cyclone in the nation, according to the books, took place mainly in Illinois. The Tri-State Tornado of 1925 took life of 695 citizens in the three states; and 613 of the fatalities lived in Illinois.
Because of the city heat island phenomenon, towns of Illinois are likely to be at 2 °F (1 °C) on a standard day, which is most visible during the night.
The maximum temperature observed in Illinois was 117 °F (47 °C), noted on July 14, 1954, at East St. Louis. The 1995 Chicago heat wave was one among the most horrible weather connected catastrophe in the history of the state , with 525 dead within a period of five days as during the night temperature increased as high as 84 °F (29 °C) and afternoon temperature increased to 106 °F (41 °C). The most lethal heat wave in the records of the United States hit Illinois during the month of July 1936, which tooklife of 2656 citizens.
Acute temperature alterations can happen within a little time with the passing of a sturdy cold wave throughout the state of Illinois. On December 20, 1836, temperatures reduced to 40 degrees Fahrenheit within minutes, which forced the people to stay in their lumbers and animals in their dens. The lower most temperature was recorded to be −37 °F (−38.3 °C), observed on January 15, 2009, at Rochelle. On the other hand, the certified noted lower most temperature of the state of Illinois is -36 degrees Fahrenheit, observed at Congerville on 5th January 1999. Protracted cold wave had hit the higher Midwest between the period of January 30 and February 5, 1996, and the low temperatures for that time averaged at −25 °F (−31.7 °C) all along the northwest area of the Illinois.
Standard yearly rainfall for Illinois ranges from approximately more than 48 inches (1,200 mm) at the southern edge to somewhat below 32 inches (810 mm) in the northern part of the state. May and June are the months of the year when the states receive maximum rainfall. Torrent and floods are the most harmful weather dangers of the state. Augmented temperature in the metropolitan heat islands guides to an increment in precipitation. Lake Michigan results to an increment in winter rainfall by the length of its south coast. During the summers, the comparatively cooler ponds guide to a steadier environment close to the lake coast.
Whilst the standard yearly snowstorm goes beyond 38 inches (970 mm) in Chicago, the southern part of the state usually gets less than 14 inches (360 mm). The winter with maximum snowfall for the city of Chicago was 89.7 inches (228 cm) throughout the winter of the year 1978/1979. Throughout thewinter season of the years 1830 and 1831, southern parts of the Illinois were coated with approximately 3 feet (or 0.91 m) of snow. Snowstorms going beyond the average of usualwinter season are probable within a single day. The maximum snowfall observed during the current times for Chicago was approximately of 23 inches (or 580 mm) within 10 hours on January 26, 1967.
Thunderstorms are accompanied with over half of the yearly rainfall all over the state. Most of the tornado and cyclones strikes between the months of April and June. Not only this, Illinois also gets the residuals of tropical cyclones which have hit the coasts of the Gulf. One of the rainiest storms, Tropical Storm Claudette, had hit the state during July 1979 getting the rainfall total of up to 7.64 inches (or 194 mm).