Hot weather, thunderstorms, lightning strikes, mudslides and brush fires kept Southland residents on edge Wednesday as a heat wave drove up temperatures and humidity levels, and more of the same is on tap for tomorrow.

Triple-digit temperatures baked much of the region, with even downtown Los Angeles flirting with the 100-degree mark.

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The mercury climbed over 100 in typical hot-weather areas such as Long Beach, Van Nuys, Chatsworth, Whittier and Woodland Hills, according to the National Weather Service.

"Today and tomorrow continue to look like the peak of the temperatures, some locations a bit higher today and some a bit higher tomorrow, with slight cooling into the weekend," according to the NWS.

"Humidity levels will remain elevated into the weekend so even with slightly cooler temperatures it will not feel as though there is much of a difference. "Elevated moisture levels and marginal instability through Saturday will keep a slight chance of thunderstorms and showers in Los Angeles County mountains ...," forecasters said.

Thunderstorms brought heavy downpours in the northern reaches of Los Angeles County this afternoon, and lightning strikes set off a series of small brush fires that kept fire crews jumping. The downpour also caused a mudslide that forced the closure of Agua Dulce Canyon Road near the Antelope Valley (14) Freeway.

Things will cool down a bit over the weekend, although temperatures will remain above normal, forecasters said. Temperatures during the rest of the heat wave will be running 10-15 degrees higher than normal, said NWS meteorologist Kathy Hoxsie. The high heat was being attributed to high pressure over the region, combined with the fact that only weak winds are blowing in from the ocean.

An excessive heat warning will remain in effect for the San Gabriel and Santa Monica mountains in both Los Angeles and Ventura counties and the San Fernando, San Gabriel and Santa Clarita valleys until 8 p.m. Thursday.

Another major factor in today's weather was the moisture flowing from Hurricane Linda in the Baja California area. The high heat coupled with the elevated humidity also prompted health concerns.

Forecasters said those at greatest risk of suffering heat-related ailments were infants, the elderly, the homeless, outdoor workers, people taking part in outdoor activities in the heat, and pets without access to shade.

They urged residents to drink plenty of water; wear light-colored and lightweight clothing; stay out of the midday sun; check on neighbors and the elderly to make sure they are not being overwhelmed by the heat; and never, ever leave children, the elderly, or pets in a vehicle parked in hot weather. Thursday's highs will be about the same as today or minimally lower, but Friday's will be several degrees lower -- around 5 degrees in many communities.