Local Climatological Data Summary: Hillsboro, Illinois, 1895-1993

Abstract

Hillsboro (Montgomery County) has a temperate continental climate, dominated by maritime tropical air from the Gulf of Mexico from about March through November. Gulf air generally supports relative humidities of about 50 to 60% during the day and 85% at night. This is the airmass which yields a "muggy" environment and promotes thunderstorms, heavy showers, and at times, damaging winds, hail and tornadoes. During these months, there are occasional, brief interruptions of drier, cooler air from the Pacific Ocean, but they typically only last for a few days.