Muggy weather could make SLO County feel like an ‘enormous sauna’ this week

Strong northwesterly winds on Sunday afternoon will hold most of the Central Coast near seasonal temperatures, and as high pressure strengthens and winds ease, daytime highs will climb through midweek.

By Thursday, an influx of monsoonal moisture from the south will bring increasing mid-and-high level clouds, warmer overnight lows and a chance of rain showers. Overall, the air will feel noticeably muggy.

Fresh to strong (19 to 31 mph) afternoon northwesterly winds this weekend will produce slightly below seasonal temperatures and mostly clear skies during the late morning and afternoon, with the marine layer returning during the overnight.

The northwesterly winds will decrease Monday through Wednesday to gentle to moderate (8 to 18 mph) levels as an upper-level, high-pressure system builds over California.

This condition will result in warmer temperatures with the inland valleys (Paso Robles) reaching the high 90s to low 100s on Tuesday and Wednesday.

Meanwhile, the coastal valleys (San Luis Obispo) will climb into the mid-80s, and the beaches will see temperatures ranging from the high 60s to the low 70s. On Tuesday and Wednesday, the marine layer with pockets of fog and mist will return during the overnight and morning along the coastline.

A weak, low-pressure system off the coastline will bring monsoonal moisture from the south. This will produce increasing mid-to-high level clouds, warmer overnight temperatures and possible rain showers on Thursday, with a greater chance of rain and thunderstorms next weekend.

Higher dew point temperatures could morph the Central Coast into an enormous sauna with convective rain showers and thunderstorms.

Temperatures are expected to decrease on Thursday and into the following weekend; however, the higher dew point temperatures will make the conditions feel more uncomfortable.

Looking further ahead, the arrival of the autumnal equinox — the beginning of fall — will occur at 11:18 a.m. Sept. 22, when the sun will be directly over the equator.

We will lose the most significant amount of daylight of the year on that day, about three minutes at our latitude. For next week, the forecasts point to increasing northwesterly winds and cooler weather.

At 4 p.m. on Friday, I will be on the Dave Congalton Show on KVEC Radio for the “Guess the First Day of Rain” Contest.

Call 805-543-8830 during the show to predict the first day the Central Coast will receive at least 1 inch of rain over 24 hours at any calibrated rain gauge in the region, such as Cal Poly, the Santa Maria Airport or the San Luis Obispo County Regional Airport.

Surf report

Gale-force northwesterly winds along the coastline will generate a 5-to 7-foot northwesterly (300-degree, deep water) sea and swell (with a 5-to-12-second period) through Sunday.

Decreasing northwesterly winds will allow a 4-to-6-foot northwesterly (295-degree, deep water) swell (with an 8- to-11-second period) to develop on Monday, lowering to 2-to-4-feet on Tuesday through Wednesday.

This northwesterly swell will increase to 3-to-5-feet with the same period on Thursday through next Saturday.

A 1-to-3-foot Southern Hemisphere (200-degree, deep water) swell (with a 15-to-17-second period) will arrive along our coastline on Tuesday and remain at this level through Wednesday, fading away on Thursday.

A marine heat wave will allow seawater temperatures to warm to 57 to 59 degrees through Monday, further heating to 62 to 64 degrees on Tuesday and remaining at this level through next weekend.

On this date in weather history (Sept. 14)

1970: The temperature at Fremont, Oregon, dipped to 2 degrees above zero to equal the state record for September set in 1926.

1988: Hurricane Gilbert made the first of its two landfalls in Mexico, producing 170 mph winds at Cozumel.

2009: A weak cold front passed San Luis Obispo County early that morning, producing light rain in the North County. The Paso Robles Municipal Airport recorded 0.06 inches of rain while Atascadero reported 0.03 inches of rain. San Luis Obispo and most areas southward only recorded a trace or no rain at all.

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

SUNDAY: 54, 91

MONDAY: 55, 93

TUESDAY: 57, 97

WEDNESDAY: 61, 101

THURSDAY: 60, 99

FRIDAY: 58, 98

SATURDAY: 57, 91

SUNDAY: 54, 85

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

SUNDAY: 55, 79

MONDAY: 58, 81

TUESDAY: 59, 85

WEDNESDAY: 62, 87

THURSDAY: 61, 86

FRIDAY: 58, 81

SATURDAY: 56, 76

SUNDAY: 55, 74

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