RIVERSIDE (CNS) - Cooler temperatures are expected throughout Riverside County to start the week, according to the National Weather Service. A trough of low pressure will move through central California through Tuesday and cause temperatures to drop to within 5 degrees of seasonal averages, forecasters said. On Wednesday and Thursday, a ridge of high pressure will move through the region and bring warmer temperatures before the region cools off again heading into the weekend. High temperatures today could reach 104 degrees in the Coachella Valley, 97 in the San Gorgonio Pass near Banning, 93 in Riverside, 91 in Lake Elsinore, 87 in Temecula, 93 in Hemet and 80 in Idyllwild. Highs in the Coachella Valley are expected to drop to 103 on Tuesday, then 102 on Wednesday, according to the NWS.