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

Forecast models indicate excessive temperatures will persist across the southwestern US through at least Oct. 7. Temperatures of around 38-44 C (100-112 F) are forecast across the affected area over the coming days.

As of late Oct. 3, the National Weather Service (NWS) has issued excessive heat warnings across western and central Arizona, western southern, and east central California, and far southern Nevada. Heat advisories are in place across most of the rest of the affected area. The excessive heat warnings and heat advisories affect around 35 million people from central Arizona to the Bay Area of California, where widespread moderate to extreme heat risk is forecast due to record-breaking temperatures. 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 a higher 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 an issue. 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.