Mondays heat shattered a 47-year record for the date in San Luis Obispo when the thermometer zoomed to 104 degrees at Cal Poly.
The previous high temperature for Oct. 1 was 95 degrees, set in 1965, said local weather expert John Lindsey.
It was hot all over Monday: Paso Robles was 105, falling short of the record of 108. Atascadero was 104. Los Osos was 85, the warmest mark there since March of 2011, Lindsey said. Morro Bay was also 85, while Cambria was 99 and Cayucos was 96.
One of the hottest spots was west of San Luis Obispo, where it reached 110 degrees at the headquarters of SLOWeather.com, a private online weather data provider.
Normally, San Luis Obispo would experience a high of 74 on Oct. 1, Lindsey said. So Mondays reading exceeded that by 30 degrees.
The cause was high pressure that sent warm, dry air from the interior of California and even Nevada westward over the Santa Lucia Mountains, Lindsey said. The air got even hotter as it flowed downhill and compressed before arriving in the coastal valleys, he explained.
Today should be another warm day, but possibly a little cooler as the high pressure is starting to break down. Lindsey said more cooling should occur Wednesday and Thursday, and by Friday onshore winds will be back in force, bringing fog and below-normal temperatures. Highs Friday and during the weekend will fall into the 70s countywide.