Sonoma and Napa counties narrowly missed being added to the areas the National Weather Service placed under a heat advisory on Monday, even as temperatures reached triple digits across the region – a forecast expected to come into effect Tuesday in the North Bay will stop.

The temperature in Santa Rosa peaked at 98 degrees Monday amid the two-day heat wave, according to the weather service’s Bay Area office.

On Monday, the city of Napa reached 97 degrees, the Charles M. Schulz-Sonoma County Airport reached 100 degrees and areas near Cloverdale reached highs of 101 degrees.

These readings were comparable to conditions in the East and South Bay, where a heat advisory remains in effect through Tuesday evening.

However, the North Bay avoided the warning as low temperatures were expected to reach 60 degrees on Monday and Tuesday. Low temperatures in these other areas were expected to bottom at 70 degrees.

“It’s a matter of how long (the heat) lasts and when to expect relief,” Braydon Murdoch, a meteorologist with the National Weather Service, said of the heat warning’s coverage area. “That’s why it’s a little more dangerous for the health of locals in these areas.”

Conditions on Monday did not reach record-breaking levels in Sonoma and Napa counties.

According to the National Weather Service, the highest temperatures ever recorded were 105 and 106 degrees, respectively, in Napa and Santa Rosa on September 23, 1939.

On September 24, Santa Rosa reached 102 degrees in 1936 and Napa reached 104 degrees in 1964.

Current conditions could contribute to fires like the 11.4-acre Antonio Fire that burned south of Petaluma Monday afternoon, fire officials said.

It was reported on San Antonio Road around 1:15 p.m. and continued to spread until 1:39 p.m. The exact cause is currently being investigated.

“Dead fuels, like the grass in which this fire burned, generally become more flammable during the first half of this week,” said Jason Clay, a Cal Fire spokesman.

Reach Staff Writer Colin Atagi at [email protected]. On Twitter @colin_atagi