RIVERSIDE (CNS) – Temperatures will soar well into the triple digits today in the Coachella Valley amid a heat wave that will keep highs past the century mark through Friday, according to the National Weather Service.

High pressure will strengthen over the next two days, making today and Wednesday the hottest days of the week, forecasters said. A slow cooling trend will follow and temperatures are expected to return to around seasonal average by Sunday.

The NWS issued an excessive heat warning that will last until 9 p.m. Thursday in the Coachella Valley.

High temperatures today could reach 91 degrees in Riverside, 107 in the Coachella Valley, 95 in the San Gorgonio Pass near Banning, 84 in Idyllwild, 94 in Lake Elsinore, 85 in Temecula and 96 in Hemet.

Nighttime lows are expected to remain in the low- to mid-70s through Thursday in the Coachella Valley, meaning the minimal cooling at night could pose a health risk to those who don’t have access to air conditioning because the body needs time to cool down from the day’s heat, according to the NWS.

The combination of hot days and warm nights is expected to increase the threat of heat illness, and the NWS urged residents to drink plenty of fluids, stay out of the sun and check up on relatives and neighbors.

High temperatures in the Coachella Valley are expected to drop to 105 on Wednesday, then decrease to 102 on Thursday and 100 on Friday, forecasters said. Highs in the Riverside metropolitan area could rise to the mid-90s on Wednesday, then drop to the mid-80s to high-80s through Friday.