SLO County weather: Warm, sunny days may give way to rain during monsoon season

A trough of low pressure along the California coastline will continue to produce gentle to moderate (8 to 18 mph) northwesterly winds, plenty of marine low clouds with areas of fog and mist in the coastal regions, and average seasonal temperatures this week.

Persistent onshore flow from the Pacific Ocean will allow the marine layer to develop in the coastal regions during the night and morning, partially clearing during the afternoon through this upcoming week. The inland valleys will remain mostly clear.

Over this period, temperatures will remain normal for August, with the inland valleys (Paso Robles) warming to the mid to high-90s, while the coastal valleys (San Luis Obispo) will reach the high-70s.

Due to warmer seawater temperatures, the beaches will range from the low to mid-60s.

August and September is the season for the North American monsoon. The remnants of another tropical cyclone off the coast of Mexico are expected to stream northward over the Central Coast on August 23, 24, and 25, producing widely scattered rain showers and a chance of thunderstorms.

The long-range weather models still do not indicate any Santa Lucia (northeasterly) wind events as a thermal low remains over the Central Valley, and the Eastern Pacific is anchored about 1,200 west of San Luis Obispo County.

Surf report

A 4- to 6-foot northwesterly (290-degree, deep-water) swell (with an 8- to 12-second period) is expected along our coastline on Sunday and will remain at this level through Saturday.

Combined with this northwesterly swell will be a 1- to 2-foot Southern Hemisphere (230-degree, deep-water) swell (with a 15- to 17-second period) on Sunday through Wednesday.

Decreasing northwesterly winds along California’s coast have produced less upwelling which in turn has allowed the ocean along our coastline to warm up. Seawater temperatures will range between 57 and 59 degrees through Monday, increasing to 59 to 62 degrees on Tuesday through Saturday.

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS