Fall arrived this week, but San Diego residents won’t be waking up to crisp and cool temperatures anytime soon. A high pressure system will hover over the region through the middle of next week, according to the National Weather Service, bringing single-digit humidity, triple-digit heat, and light offshore winds – the key ingredients for wildfires.
Rob Balfour, senior forecaster with the National Weather Service in San Diego, said strong Santa Ana winds won’t be a factor, but dry heat and offshore breezes will be enough to create "a critical fire danger."
“Humidities will be low," said Balfour. "They’ll most likely be below 10 percent and that certainly is critical," he said.
Balfour said high fire conditions occur when humidity levels drop below 15 percent. "And below 10 percent, fires tend to take off and grow very rapidly,” he warned. He added that remaining moisture in some plants may help deter major wildfires this weekend.
“We still have relatively high fuel moisture in the live fuels," he said.
Balfour said the grasses have dried out and died, and some of the smaller chaparral is getting into the critical moisture stages. "But for the most part, in the mountains the timber and the larger brushes are still not quite to critical levels," he explained.
Sunday and Monday are expected to be the hottest days, according to Balfour, with temperatures in the inland valleys soaring above 100 degrees, and 30 mph wind gusts in the canyons and passes. Coastal areas will have temperatures in the upper-80s.
Balfour said a high pressure pattern over the region, combined with dry brush, is expected to bring above-normal fire activity to San Diego throughout October.
