A lengthy heat wave gripping California shows no signs of letting up this weekend for most of San Diego County, prompting the National Weather Service to extend a heat warning for the inland valleys for another day.
Meanwhile, a Flex Alert urging Californians to conserve electricity to prevent overtaxing the grid system was extended through Friday as extreme heat continues to grip the region leading to an extension of a heat warning for the inland areas.
Friday was the fourth day of a grueling heat wave that sent temperatures soaring about 10 to 20 degrees above normal for this time of year.
An excessive heat warning that has been in effect since Tuesday was set to expire Friday evening for San Diego County’s inland valleys and foothills, but was extended through Saturday. Heat warnings will stay in effect until Saturday for the mountains and Sunday in the desert.
On Thursday, the Borrego desert broke a high-temperature record with a reading of 118 degrees. Its previous record was 114 degrees set in 1965. On Friday, the desert could reach up to 122 degrees.
Along the coast though, there will be some relief. The same weather system was bringing a layer of thick clouds to the coastal communities on Friday, bringing down the extreme temperatures from earlier. With it came the possibility for isolated and brief thunderstorms, mostly in North San Diego County.
Expect the same weather pattern through the weekend -- cloudy but muggy along the coast, hot inland and scorching east of the mountains. But good news is ahead, NBC 7 Meteorologist Sheena Parveen says.
"We finally cool down next week."
What is a Flex Alert?
The California Independent System Operator (CAL ISO) first issued the Flex Alert from 5 p.m. to 10 p.m. Thursday and -- before it had even taken effect -- the agency extended the alert for another day.
A flex alert is a voluntary call to conserve energy as demand reaches a peak, typically in the hot summer months. The CAL ISO monitors energy usage and as demand approaches available capacity, a flex alert is issued. Track available capacity here.
Consumers should conserve electricity by turning off unnecessary lights, not using major appliances and setting air conditioner thermostats to 78 degrees or higher, especially in the late afternoon and early evening when the grid is most stressed, the ISO said.
More energy-saving tips can be found on the FlexAlert website.
What Is a Heat Wave?
San Diego County knows heat waves all too well, but NBC 7 meteorologist Dagmar Midcap said it is a bit early in the year for a hot weather pattern of such intensity. She said it’s all leading toward a warming trend, and she breaks it down here.
Midcap said a heat wave can be defined as unusually hot temperatures that last for at least two days. A heat wave builds slowly and can last for well over a week. It can happen with or without humidity.
With Intense Heat Comes Fire Danger
The NWS said the hot temperatures are expected to bring elevated fire danger to the region, especially in the peak of the afternoon. Not helping the situation is the potential for isolated thunderstorms with possible lightning strikes and gusty winds. Luckily, by Thursday, temperatures were expected to cool slightly.
Cal Fire said the county has already seen a 26% increase in fires and the acres burned are 58% higher compared to this time last year.
Due to the excessive heat, Cal Fire has shut down popular hiking trails in the Cleveland National Forest (Cedar Creek Falls and Three Sisters Falls Trailhead), where they tend to have more rescues.
Safety Tips: How to Beat the Heat in San Diego County
“If you see folks profusely sweating, they have a rapid heart rate, they feel nauseous or dizzy and then the sweating stops, heat illness is actually taking effect and it can happen rather quickly,” Cal Fire spokesman Capt. Frank Lococo said.
Parveen also outlined some important heat safety tips here. This includes:
- Drink lots of water
- Take breaks from the sun/being outside
- Check on the elderly
- Wear lightweight, loose clothing
- Never leave children or pets alone in cars – it gets so hot in there, so quickly
"Please make sure your pets and livestock have cool water to drink and someplace to take shelter from the heat," Parveen said. "Remember: Never leave kids or pets in a hot car. Walk your pets in the morning and evening; pavement can be 40 to 60 degrees above the air temperatures. That's near 130 degrees and hot enough to fry an egg, let alone burn little paws!"
San Diego County will open its Cool Zones for the 2021 summer season to both humans and service animals starting June 15. Here’s a list of local Cool Zones where you can find some respite from the heat.
UV Index and Sunburns
During extreme heat like this – and when the sun angle gets higher, on or around summertime – the UV index also gets higher.
Parveen explains the UV index here, and how it’s much easier to get sunburns under these conditions.
Sunburn potential is at its peak in the summer because the sun’s rays are stronger, especially during the middle of the day. Parveen said those who are exposed to sun at that time could get a sunburn within 10 to 15 minutes, when the sun angle is at its strongest.
She said sunblock that is SPF 30+ or higher is the way to go.
Now, what about the heat index?
According to the National Weather Service, the heat index is also known as the apparent temperature – or what the temperature feels like to the human body when relative humidity is combined with the air temperature.
But, because the air in San Diego County is so dry, Parveen said our region isn’t in a place where heat index – factoring in relative high humidity – is much different than the actual temp in the air.
“We are in a Mediterranean climate, which is dry and hot in the summer,” she explained.