A dangerous heat wave is expected to hit Southern California this weekend, with the warmest temperatures forecast for Friday and Saturday, the National Weather Service said.

An excessive-heat watch is in effect for much of southwestern California for those days, the weather service said. Temperatures in the valleys, the lower mountains and desert locations are expected to range between 102 and 112 degrees. Parts of the coast could reach around 100 degrees.

The heat will be accompanied by very dry conditions, forecasters said, with the potential for low humidity. Northerly winds will also blow through portions of the region, with gusts up to 35 mph hitting the Santa Barbara coast.

Forecasters warned of a significant heat and fire threat and urged people to take necessary precautions.


“Stay hydrated, try to wear light clothes and light colors, and try to limit activity outside,” said Keily Delerme, a meteorologist with the National Weather Service in Oxnard. “Do not leave pets or kids in the car, even if it’s for a short period of time. It can be dangerous.”

The elevated temperatures will complicate life for thousands of firefighters now battling wildfires throughout California, officials say.

Draped in heavy turnouts, firefighters can quickly become exhausted working 12- to 24-hour shifts. While the heat beats them down, it can also add strength to the fire they’re trying to extinguish, said Anthony Brown, a spokesman with the California Department of Forestry and Fire Protection.

“It’s going to dry out the fuels on the ground and if it’s windy, that’s going to contribute to fire growth,” Brown said.


Thousands of firefighters are currently assigned to the County fire in Yolo and Napa counties, where the blaze has chewed through 86,000 acres and was 30% contained Thursday. Meanwhile, the Pawnee fire, which has burned 15,000 acres in Lake County, is 92% contained.

A two-day dip in temperatures allowed crews to make significant gains on containing both blazes, Brown said, but a return of the heat this weekend could slow the momentum.

The heat in the Sacramento valley could reach the triple digits over the weekend before dropping early next week, the National Weather Service said. A similar drop is forecast in Southern California, where temperatures are expected to fall by about 10 degrees in Los Angeles by Sunday.

“Temperatures will be above normal, but in the 80s and 90s, and in coastal areas in the 70s,” Delerme said. “It’s still going to be hot, but a few degrees less.”


Times staff writer Joseph Serna contributed to this report.

sarah.parvini@latimes.com

Twitter: @sarahparvini


UPDATES:

12 p.m.: This article was updated with comments from Anthony Brown, a spokesman with the California Department of Forestry and Fire Protection.

This article was originally published at 7:40 a.m.