An early spring heatwave is set to bring record temperatures for this time of year to much of the U.S. this week. Thanks to a strong ridge of high pressure centered over the American Southwest, temperatures in the region could hit 100 degrees F (38 C) at the earliest time of year since 1988. Across California and the desert southwest, temperatures are forecast to be 20 to 30 degrees Fahrenheit (11 to 17°C) warmer than normal for this time of year.