A period of cooling that made for a fairly temperate start to summer in the San Diego area this week will give way to intensifying heat over the next several days, according to meteorologists.
A low-pressure trough along the California coast was slowly weakening as a large ridge of high pressure built over the Pacific Northwest this weekend, bringing local temperatures 5 to 10 degrees above normal to Southern California, according to the National Weather Service.
RELATED: Weekend To Bring Increasing Heat In San Diego Area
Due to the potential for dangerously hot conditions, an NWS excessive- heat watch was in effect for the local deserts from Sunday morning through Monday evening.
The California Independent System Operator issued a heat bulletin Sunday in anticipation of increased electricity demand due to above normal temperatures across California. Potential for resource shortfalls are projected for Monday, but could be made up through voluntary consumer conservation.
If weather or system conditions worsen, the ISO may notify the public about potential energy shortages and the need to conserve. The ISO could also issue a flex alert, a voluntary call for consumers to reduce electricity use during critical times of stress on the grid.
San Diego County said the following cool zone locations would be open Sunday:
— The Borrego Springs Library, 2580 Country Club Road, open noon to 6 p.m.;
— The Santa Ysabel Nature Center, 22135 Highway 79, open 9 a.m. to 7 p.m.
Low daytime humidity levels in the arid eastern reaches of the county were expected to fall to around 10% through the weekend, forecasters said. Those conditions, combined with dry, gusty winds, will result in elevated wildfire hazards in the deserts and on the eastern slopes of the mountains.
For the early and middle part of this week, monsoonal moisture may begin to spread into the region, a development that could bring a chance of thunderstorms, mainly in the mountains and deserts and mostly during the afternoon and early-evening hours, according to the weather service.
The potential for dry lightning strikes will be greater initially in the heat wave, when atmospheric moisture will be relatively limited. The potential for rainfall may increase later in the week, meteorologists said.
