LOS ANGELES - Los Angeles County set an all-time temperature record on Sunday, with a high of 121 degrees at Pierce College in Woodland Hills.
It was the highest temperature ever observed at an official recording station in the county, according to the National Weather Service.
Record or near-record temperatures were being felt for a second straight day across the Southland as a blistering holiday weekend heat wave maintained its stranglehold, with no significant relief expected until after Monday.
An excessive heat warning was in effect until 8 p.m. Monday for L.A.and Orange County.
Downtown Los Angeles reached 111 degrees, just two degrees short of the all-time record set in 2010. Other cities were also approaching all-time highs, with Van Nuys and Santa Clarita each reaching 116 and Burbank 114.
Orange County wasn't being spared either, with Anaheim and Fullerton both expected to exceed 110 degrees by late afternoon.
Cooling centers were open throughout the weekend in both counties and can be found at https://ready.lacounty.gov/heat/ and www.211oc.org/resource-centers/extreme-heat-cooling-centers.html.
Officials cautioned that capacity is limited due to social distancing requirements.
"These highs on Saturday and Sunday will be about 15-25 (degrees)above normal across the region," according to an NWS statement.
"Temps will become dangerously hot for most areas, even over the coastal plain away from the beaches Saturday and Sunday.
This kind of heat can be life-threatening and people are urged to use common sense, keep hydrated and stay out of the heat and in air-conditioned locations as much as possible."
The heat wave wreaked havoc on the local power grid, with Southern California Edison and the Los Angeles Department of Water and Power reporting scores of scattered outages that left thousands of people without electricity all day long.
Some DWP customers were not expected to have their power restored until Monday.
The California Independent System Operator, which manages the power grid, announced that a Flex Alert -- a call for voluntary conservation -- will be in effect from 3 to 9 p.m. through Monday.
Urging voluntary conservation is an effort to stave off too much strain on the state's electrical system, possibly leading to rolling power outages, like those that occurred during high heat last month.
However, state officials said later Sunday that rolling blackouts were possible Sunday afternoon, as the state was expected to near its all-time record for energy demand.
The high heat is being attributed to high pressure, which is forecast to settle into the Great Basin area through the weekend.
In forecasting an increased fire danger, forecasters said they were mainly focusing on the dryness that will take hold in the region, partly because of the absence of monsoonal moisture.
Forecasters said humidity levels would fall to single digits in interior areas of L.A. County, and a red-flag warning for increased wildfire danger was in effect through 10 p.m. Monday for the L.A. County mountains.
Several brush fires broke out Sunday, including a 500-acre wildfire burning near Cogswell Dam in the Angeles National Forest. Structures were being threatened, and drivers were urged to avoid Highway 39 so it can be used exclusively for emergency vehicles.
Smoke from that fire was seen for miles and was contributing to unhealthy air quality in the region.
All residents were urged to avoid strenuous activity and stay indoors as much as possible.
Authorities advised that children, seniors and pets must never be left unattended in vehicles under any circumstances since temperatures can quickly turn lethal in the current conditions.
The heat was expected to ease by about 10-12 degrees on Monday, but still remain above 100 degrees in many areas.
More significant easing as expected the rest of the week, with temperatures mostly in the mid-to-upper 90s in all but the warmest areas of the valleys.