Map from the National Weather Service shows the areas of 'excessive heat' alerts in California.

The rest of the nation has sweltered this summer, but California has escaped extreme heat — until now. The National Weather Service may not have high-end graphics, but its map tells the story. The San Joaquin Valley, starting south of Modesto, is colored a brownish-red and that means excessive heat warning. Temperatures are expected to exceed 100 degrees every day until Tuesday. The bright pink areas indicate a heat “watch” (click here if you don’t know the difference). This kind of heat is not just a weather story, it’s a significant health and environment story too.

High heat is hazardous to people, pets and livestock. San Joaquin County Public Health Services warns people to drink plenty of water, stay cool in an air-conditioned room and wear loose-fitting clothing. And, please, do not leave children, seniors or pets in a parked car for any period of time, even with windows cracked. The interior of the car can heat up very fast — to deadly levels — within minutes.

Those at highest risk for heat stress are children under age 4, adults with disabilities, anyone with a chronic illness and the elderly.

With high heat generally comes higher pollution which puts people with respiratory conditions at risk as well. Kevin Hall, Director of the Central Valley Air Quality Coalition emailed me that the worst air is likely to be in the Fresno metropolitan area and “presumably, up against and into the Sierra Nevada — but we only have the forest service monitors at 1500 and 5500 feet in eastern Tulare County.” He also pointed out that the Valley Air Board suspended issuing “Spare the Air” days three years ago, so air quality warnings will not be issued.

Indeed, when I checked the Valley Air Board’s website, it showed today’s air quality forecast as “moderate” even though numbers from the state Air Resources Board show that yesterday’s 8-hour ozone levels exceeded both state and federal standards in many areas in and around Fresno.

Finally, this kind of heat stressed humans and the state’s power grid. The California Independent System Operator has issued a Flex Alert starting tomorrow and running through Sunday. People are encouraged to reduce their energy use, especially in the afternoon. As Steven Greene told KPBS, “During the 4 to 6 p.m. period, we like to call that the ‘air conditioning rush hour.’ Many people come home and they have been out in the weather and want to cool down fairly quickly. So they go over their thermostat to do that.”

Greene says a setting of of between 70 and 80 degrees provides enough cooling and helps lessen the energy strain.