US: High temperatures forecast to persist across western regions through at least Sept. 7 /update 1

Forecast models indicate excessive temperatures will persist across parts of the western US through at least Sept. 7. Temperatures of around 41-47 C (105-117 F) in the Desert Southwest and around 35-41 C (95-105) in southern and central California and the Pacific Northwest are possible Sept. 4, with even higher maximums possible Sept. 5. The area of high pressure responsible for the heat is forecast to weaken from Sept. 7 as a storms system moves southeastward from the Gulf of Alaska toward the northwestern US.

As of early Sept. 4, the National Weather Service (NWS) has issued excessive heat warnings across parts of southern California, southern Nevada, southern and western Arizona, western Oregon, and southwestern Washington. Heat advisories are in place across much of the rest of the affected area. Officials could update and extend the coverage of weather alerts over the coming days.

The high temperatures may result in increased energy and water demand and an increased risk of heat-related illnesses such as heat exhaustion and heat stroke. Authorities advise the general public to avoid prolonged exposure to direct sunlight, wear loose and light clothing, and stay hydrated.

The extended period of oppressive heat and dry conditions may produce ideal circumstances for wildfire growth throughout the region. Heatwaves also pose a threat to vulnerable groups - such as the elderly, children, pregnant women, and those with respiratory illnesses - due to the increased possibility of heat stroke or heat exhaustion during prolonged exposure to high temperatures. These health risks could also extend to relatively healthy individuals during significant heatwave events.

High temperatures may warp rail tracks and force passenger and freight trains to operate at reduced speeds. Road surface damage is also possible, and overheated vehicles may worsen traffic problems in urban areas where congestion is already a problem. Commercial trucking disruptions might occur as very high temperatures put more stress on vehicles, making tire blowouts more common. Major flight disruptions are unlikely, but general aviation disruptions are possible, and some airfreight carriers could reduce cargo loads. High temperatures could lead to an increased demand for electricity, which might trigger localized brownouts or blackouts, exacerbating hazardous conditions when air conditioning is no longer possible.