Record-breaking early heat wave hits Pacific Northwest and West Coast.

Large parts of the Pacific Northwest are experiencing an early heat wave, with temperatures up to 30 degrees above normal. Experts warn that early-season heat waves can pose health risks to people who have not had a chance to build tolerance to heat. Acclimatization to increased temperatures requires at least two hours of exposure to heat for a period of four to 14 days. The population groups most vulnerable to extreme heat include the elderly, small children, outdoor workers, and pregnant women. The expected heat wave in the Pacific Northwest was made two to five times more likely by global warming.