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Abstract Wind chill temperature (WCT) is a widely recognized biometeorological variable that quantifies atmospheric conditions that have consequential impacts on many aspects of society, especially human health through exposure to winter conditions that can result in hypothermia, frostbite, and cardiorespiratory mortality. The spatial and temporal variations in WCT and extreme WCT (E WCT) (coldest 1%) were examined using hourly surface measurements collected at 133 stations across Canada and the United States during 40 winters (1979/80–2018/19). Most locations experienced an overall warming in both mean and extreme WCTs. The most substantial and statistically significant warming of mean WCT occurred across Alaska and the Canadian Northwest Territories with values of +3.2° to +6.4°C during the 40-winter time period. Statistically significant warming of mean WCT also occurred along the East Coast of Canada and the United States, as well as across the southeastern United States. Extreme WCT was found to be 10°–30°C colder than the mean WCT, and generally, the extreme WCT warmed at a greater rate than the mean WCT at locations. For example, extreme WCT warmed as much as +10.4°C during the 40-winter time period across portions of Alaska and the Canadian Northwest Territories. Warming air temperatures were found to have a large relative contribution to warming of mean and extreme WCTs with a smaller contribution coming from decreasing wind speeds (WS). 

In the Great Lakes region, total cold-season snowfall consists of contributions from both lake-effect systems (LES) and non-LES snow events. To enhance understanding of the regional hydroclimatology, this research examined these separate contributions with a focus on the cold seasons (October–March) of 2009/2010, a time period with the number of LES days substantially less than the mean, and 2012/2013, a time period with the number of LES days notably greater than the mean, for the regions surrounding Lakes Erie, Michigan, and Ontario. In general, LES snowfall exhibited a maximum contribution in near-shoreline areas surrounding each lake while non-LES snowfall tended to provide a more widespread distribution throughout the entire study regions with maxima often located in regions of elevated terrain. The percent contribution for LES snowfall to the seasonal snowfall varied spatially near each lake with localized maxima and ranged in magnitudes from 10% to over 70%. Although total LES snowfall amounts tended to be greater during the cold season with the larger number of LES days, the percent of LES snowfall contributing to the total cold-season snowfall was not directly dependent on the number of LES days. The LES snowfall contributions to seasonal totals were found to be generally larger for Lakes Erie and Ontario during the cold season with a greater number of LES days; however, LES contributions were similar or smaller for areas in the vicinity of Lake Michigan during the cold season with a smaller number of LES days. 

Abstract Adverse weather has been shown to be spatially and temporally variable across high‐latitude locations. The current study provides a unique investigation of limited surface visibility time periods at five coastal Greenland locations from 1979 to 2018 and identifies the coincident adverse weather, as well as the local and large‐scale atmospheric conditions during limited surface visibility time periods. Locations on the east coast of Greenland have the largest percentage of hours with limited visibility each month with maxima during February. Western and southern coastal locations have fewer occurrences of limited visibility. Warm‐season maxima are present in the northern locations, while warm‐season minima occur at all other locations. Fog is reported during each month at all five stations, however, a substantial increase of hours occurs at the northern and eastern stations during the typical melt season on Greenland. There is a seasonal difference in the percent of limited visibility hours linked to precipitation with a minimum in the warm season and maximum across the cold season. Limited visibility attributed to precipitation generally has the largest percentage of hours each month except for the northern and eastern locations during the melt season. The location and number of cyclonic circulations, as well as the spatial scale of troughs, across northeastern Canada and the North Atlantic Ocean greatly influence the adverse weather linked to prolonged limited surface visibility events. Limited visibility events at Thule, Greenland during both the warm and cold seasons are largely influenced by the presence and intensity of a cyclone over northeastern Canada. At Danmarkshavn, Greenland limited visibility events in both seasons generally have a cyclone positioned to the east, an area of higher pressure over Greenland and a cyclone positioned to the west of Greenland.