Seasonal and Diurnal Variation of Wind Chill Temperatures

Extreme wind chill temperatures (WCTs) can pose a significant risk to people, agriculture, and livestock. WCT has been investigated for some areas in the United States (e.g., Central Plains) and around the world (e.g., Patagonia), but not at a continental scale. Data were used from 160 hourly reporting surface stations that included at least 70% of hourly observations for the winters (Nov., Dec., Jan., Feb., Mar.) of 1970/1971 through 2013/2014. This specific project examines the seasonal and diurnal variations of WCT for a small subset of station pairings in the Continental United States, where stations in the pairings differ in location with respect to elevation and relative distance to coastline. Analyses show a general seasonal trend in WCT for all the stations, with the colder and most extreme WCTs occurring in January and the inland, higher elevation locations along the East Coast having colder median WCTs compared to paired coastal locations. Nearly all stations have a distinct diurnal variation of WCT with the most frequent and coldest WCTs having occurred in the early morning, during the sunrise period for that respective location, and the least frequent, warmer WCTs having occurred in the late afternoon, just before sunset. An extreme WCT event on 20-21 January, 1985 in the Southeastern United States was also examined to understand diurnal variations and evolution of the synoptic weather pattern.