After unusually cool summer, SLO County could heat up next week. See forecast

For most of this July, the atmosphere has remained stuck in a stubborn pattern: a dominant high-pressure system over the Central U.S. has fueled relentless heat and humidity east of the Rockies, while a series of low-pressure troughs along the West Coast have kept our temperatures cooler than normal.

At the Paso Robles Airport, where the average July temperature is typically 72 degrees, this month has averaged just 69 degrees. In fact, there’s no record of a California Mid-State Fair that didn’t hit 100 degrees at least once — and this year it did not.

The last time Paso Robles reached triple-digit levels was on July 11, when the mercury soared to 103 degrees.

In Santa Maria, the monthly average so far is 62 degrees, two degrees below the normal 64 degrees. Along the coast, my weather station in Los Osos is holding steady at 57 degrees — also about two degrees cooler than average for July.

A gradual shift in the weather pattern is expected over the next few weeks as high pressure slowly builds along much of the West Coast.

Fresh to strong (19 to 31 mph) northwesterly winds will continue each afternoon, easing overnight and into the morning. These winds will bring in widespread coastal marine stratus clouds to the coastal regions during the overnight with morning fog, mist and occasional drizzle throughout the week. The inland valleys should remain clear.

Despite this persistent marine influence, the afternoon northwesterly winds should be strong enough to clear the marine layer, leaving generally sunny skies with occasional patches of mid- to high-level clouds from sporadic surges of subtropical moisture from the southeast.

High temperatures in the inland valleys (Paso Robles) will reach the low to mid-90s through Friday, warming to the low 100s next Saturday and Sunday. The coastal valleys (San Luis Obispo) will range between the low to mid-70s through Friday, warming to the 80s by next weekend.

Beach temperatures will hover in the low to mid-60s, except for the southerly facing beaches of Cayucos, Avila Beach and Shell Beach, which will hit the low 70s.

Looking ahead to the following week, increasing high pressure over California will produce hot inland temperatures with the inland valleys (Paso Robles) ranging between 102 to 107 degrees.

The coastal valleys could warm into the 90s, while most of the beaches will remain in the 60s under a thin and compressed marine layer. The Central Valley could see temperatures reaching 115 degrees by the end of next week.

Surf report

Fresh to strong (19 to 31 mph) northwesterly winds along the California coastline will generate a 3- to 5-foot northwesterly (300-degree deep-water) sea and swell (with a 5- to 8-second period) through Wednesday morning, increasing to 5- to 7-feet with the same period by Wednesday afternoon.

This 5- to 7-foot northwesterly (300-degree deep-water) sea and swell (with a 5- to 8- second period) will continue at this level through next Sunday.

Seawater temperatures:

Surface seawater temperatures will range between 58 and 60 degrees through Wednesday, decreasing to 57 to 59 degrees on Thursday through next Sunday.

On this date in weather history (July 27):

1943: On a whim, and flying a single engine U.S. Navy AT-6, Lieutenant Ralph O’Hair and Colonel Duckworth were the first to fly into a hurricane. It started regular U.S. Navy and Air Force flights into hurricanes.

1989: Thunderstorms produced locally heavy rains in the southwestern United States. Yuma, Arizona, experienced their most severe thunderstorm of record. Strong thunderstorm winds, with unofficial gusts as high as 95 mph, reduced visibility to near zero in blowing dust and sand. Yuma got nearly as much rain in one hour as is normally received in an entire year. The storm total of 2.55 inches of rain was a record 24-hour total for July. Property damage due to flash flooding and high winds was in the millions. (Storm Data)

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

John Lindsey is a retired PG&E marine meteorologist. Email him at JohnLindseyLosOsos@gmail.com or follow him on X @PGE_John.