Forecasters are warning Southern Californians to brace for an incoming heat wave, with temperatures climbing well above seasonal averages and peaking around midweek.

The National Weather Service said the hottest conditions will hit Tuesday through Thursday, with Wednesday likely to be the warmest day of the stretch.

Inland valleys across Los Angeles and Ventura counties could see temperatures rise into the low to mid-90s, while some desert communities may reach or exceed 100 degrees. Coastal areas are expected to remain somewhat cooler, with highs generally ranging from the mid-70s to low 80s.

Forecasters said the warming trend will begin Monday and intensify through Wednesday as high pressure strengthens over the region. Temperatures in inland areas are expected to run 4 to 10 degrees above normal for late June.

NWS officials issued a heat advisory from Tuesday morning through Thursday evening for portions of L.A. County, citing an increased risk of heat-related illnesses.

Officials noted that even though temperatures may fall just short of more extreme warning criteria in some areas, heat impacts could be amplified by large outdoor events and an influx of summer visitors unfamiliar with local conditions.

According to Weather Service spokesperson Carol Ciliberti, temperatures in downtown L.A. and surrounding metro areas could approach 90 degrees, while the San Fernando and San Gabriel valleys are expected to climb into the mid-90s.

The Antelope Valley and parts of Santa Barbara County’s Cuyama Valley could top 100 degrees.

“The increased temperatures bring a higher risk of heat-related illnesses, especially for the young, the elderly and those without air conditioning,” Ciliberti told The Times.

The heat wave is also expected to suppress the marine layer that has contributed to persistent June gloom conditions, leading to sunnier skies for much of the week.

Forecasters are also monitoring an unusual push of mid-level moisture expected late Tuesday into Wednesday. While the chance of measurable rainfall remains low, weather models indicate a 5% to 15% chance of light showers, mainly across L.A. and Ventura counties.

The hot, dry conditions may also elevate fire weather concerns across portions of Southern California. NWS warned that drying vegetation and the potential for large fire plumes could increase wildfire risk in valleys and mountain areas.

Meanwhile, air quality concerns remain in parts of L.A. as smoke from the ongoing Boyle Heights warehouse fire continues to affect the region. Weather officials said the shallower marine layer could contribute to poor air quality while the fire remains active.

Relief is expected later in the week. Forecast models show the ridge weakening by Thursday and into the weekend, allowing temperatures to cool several degrees each day.