Temperatures reached the triple digits in places like Burbank, Ontario, Santa Clarita and Van Nuys. Other places like Fullerton, Palmdale and Riverside reached the high 90s.
The National Weather Service said the fire danger was elevated, which was short of red-flag conditions. It was dry, but the winds were calm.
A fire broke out in the Lytle Creek area in the hot and dry conditions. The blaze charred 75 acres.
Also Monday, a brush fire burning about 10 miles north of Castaic Lake next to the 5 Freeway forced the closure of lanes.
But there was good news for people by the beach. A shallow marine layer kept the coastal plain cooler. Highs were in the mid 70s in Santa Monica, high 80s in Long Beach and high 60s in San Clemente.
A cool down is expected as the week carries on.
By 8 a.m., it was 80 degrees in Encino, where everyone from golfers to walkers and tennis players got their workouts in early.
"It's pretty bad, it's miserable," said Leonard Zambito of Encino. "I actually played tennis yesterday, so walking on the golf course is a lot easier that sweating out there on the tennis courts."
With the mercury rising, people were reminded to stay hydrated, keep out of the sun as much as possible and keep an eye on pets and the elderly.