A significant and unusually early heatwave is building across the south-western US this week, bringing temperatures more typical of early summer than mid-March. In Phoenix, Arizona, the National Weather Service (NWS) forecasts temperatures could exceed 100F (38C) as soon as Wednesday, marking the earliest arrival of triple-digit heat in nearly four decades. A strong, slow-moving high-pressure system — often referred to as a heat dome — is trapping hot air over the region, pushing temperatures 20–30F above normal in parts of California, Nevada, and Arizona.
The heat is expected to persist for several days, with limited overnight cooling adding to the strain. Millions are likely to be affected, with high temperatures expected in typically cooler coastal regions, while inland and desert locations could exceed 100F. NWS has issued heat advisories for various areas, including the Bay Area, as residents are advised to check on the elderly and at-risk groups and schedule activities around peak heat hours.
The Las Vegas NWS office has warned that this extreme early-season heat is particularly dangerous, especially for tourists and individuals not acclimated to such temperatures. Furthermore, this heatwave could lead to accelerated snowpack melt in California, posing a risk of summer water shortages and heightening wildfire season potential.
Despite the scorching conditions, the wildfire risk remains relatively low across much of the Southwest due to lighter winds, though areas near the Rockies may experience an increased threat. By week’s end, above-average temperatures are expected to spread across much of the United States.
The heat is expected to persist for several days, with limited overnight cooling adding to the strain. Millions are likely to be affected, with high temperatures expected in typically cooler coastal regions, while inland and desert locations could exceed 100F. NWS has issued heat advisories for various areas, including the Bay Area, as residents are advised to check on the elderly and at-risk groups and schedule activities around peak heat hours.
The Las Vegas NWS office has warned that this extreme early-season heat is particularly dangerous, especially for tourists and individuals not acclimated to such temperatures. Furthermore, this heatwave could lead to accelerated snowpack melt in California, posing a risk of summer water shortages and heightening wildfire season potential.
Despite the scorching conditions, the wildfire risk remains relatively low across much of the Southwest due to lighter winds, though areas near the Rockies may experience an increased threat. By week’s end, above-average temperatures are expected to spread across much of the United States.
