An intense late-summer heat wave is persisting along the U.S. West Coast even after reaching its peak on Thursday. Inland areas of the San Francisco Bay Area remained around 90°F on Friday, while forecasts called for triple-digit temperatures from California’s Central Valley northward into Washington state. The conditions forced several high-school football programs from Northern California to Washington to push back or reschedule season-opening games, with districts citing new heat-safety protocols that require play to pause when wet-bulb globe readings exceed set limits. Farther south, Arizona is contending with both heat and moisture. Phoenix recorded an 89°F overnight low at Sky Harbor International Airport on Friday, tying the city’s warmest minimum for the date, and Thursday-night monsoon storms dumped more than half an inch of rain in parts of the metro area, toppling trees and causing minor street flooding. The National Weather Service warned that additional rounds of heavier rainfall through the weekend could trigger flash flooding across northern and central portions of the state. While the West swelters, a strong cold front is sweeping into the Midwest and is expected to drop temperatures as much as 25°F below seasonal norms. Forecasters say lows could dip into the 30s in parts of Minnesota after the weekend, raising the prospect of rare late-August frost, and daytime highs in Chicago may struggle to reach 70°F early next week. The Federal Aviation Administration separately cautioned travelers to monitor flight status as thunderstorms are likely over Florida, the Gulf Coast hubs and much of the Northeast on Sunday.