A potentially dangerous heat wave is forecast to broil Southern California this week, boosting the mercury at least 20 degrees above normal, potentially toppling temperature records and raising concerns about an earlier start to the fire season.

After a mild start to the week, the region will start warming up on Wednesday with temperatures in the high 70s and low 80s across much of Los Angeles County. But the real heat will hit Thursday and Friday with temperatures reaching into the 90s along the coast and in the valleys with some areas reaching 100 degrees, according to the National Weather Service.

“Typically for March, the average high temperatures are in the upper 60s to mid-70s depending on where you are in the L.A. area, so this does put us a good 20 to 30 degrees above normal for this time of year,” said Ryan Kittell, a meteorologist with the National Weather Service in Oxnard.

The heat is expected to topple several daily temperature records across the region with some locations potentially breaking the all-time record for the month of March, according to the weather service.

Many coast and valley areas could see heat advisories on Thursday and Friday as temperatures climb. By Friday, downtown L.A. is expected to hit 98 degrees. It’s forecast to be 98 degrees in Burbank, 97 in Long Beach and 93 at Los Angeles International Airport, Kittell said.

The story is the same south of Los Angeles. Temperatures are forecast to hit 100 degrees in Anaheim, 96 degrees in Irvine and 85 degrees along the coast in San Clemente and 87 degrees in Oceanside. In San Bernardino and Riverside counties, temperatures are expected to linger in the mid- to high 90s with the mercury rising to 95 degrees in Lake Elsinore, 96 degrees in San Bernardino, 97 degrees in Palm Springs and 100 degrees in Thermal.

Temperatures are forecast to cool by a few degrees over the weekend, but it’s expected to stay hot for at least the early part of next week, Kittell said.

“The one saving grace is that overnight lows are expected to be in the upper 50s and 60s, which is still well above normal, but at least there will be several hours of overnight relief,” the weather service wrote in its forecast.

The exceptional warm-up follows a drier end to winter across Southern California. At this point, experts say, even if a fire starts, the fuels aren’t dry enough to cause a massive conflagration.

But the heat will “certainly accelerate the natural curing process where plants start to really lose their moisture,” Kittell said.

The continued heat is also likely to further diminish the state’s snowpack. The snowpack acts as a natural water storage system for California, and ideally when the region’s climate shifts from cold to warm and dry, the snow gradually melts down from rivers and creeks to fill reservoirs over a period of months.

If the snowpack melts too fast, the surge of water can overwhelm rivers and infrastructure, leading to flooding and water supply shortages later in the season.

The northern Sierra is currently at 34% of average and the southern Sierra 76% of average, down even further from last week when data showed significant losses following a late February heat wave.

California relies on the Sierra snowpack for about 30% of its water. But it’s not all bad news. The Los Angeles Department of Water and Power reported on Tuesday that the overall snowpack in the eastern Sierra was holding at 100% of normal as of March 1.

There is no rain in the forecast over the next two weeks, but there’s still some potential for moisture in April and May, and that could boost the snowpack and keep fire season at bay a little longer, Kittell said.

“I don’t think we’re at the point right now where there’s a real high fire risk ... but if this heat lingers for a long time and we don’t get anymore rain, then the fire season might come earlier rather than later,” he said.