Local Climatological Data Summary: Bloomington-Normal, Illinois, 1893-1994

Abstract

Bloomington and Normal (Mc Lean County) have a temperate continental climate, dominated by maritime polar air from the Pacific throughout most of the year, particularly spring and fall. This air is relatively dry, having lost its moisture passing over the Rockies. During summer, the dominant airmass is maritime tropical (warm and humid) air from the Gulf. This air generally supports relatively high humidities, yielding a "muggy" environment. During winter, Bloomington-Normal is dominated by an almost equal mix of Pacific air and continental polar (cold and dry) air from Canada. Canadian air is very dry and in winter brings temperatures into the single digits and negative values for a few days.