Triple-digit temps to hit Mid-State Fair. How long will heat last in SLO County?
Warm and humid weather will continue through Monday, followed by increasing northwesterly winds, low marine clouds, and cooler temperatures along the immediate coastline, but warm to hot conditions will continue in the inland and coastal valleys through the rest of the week.
High pressure near the Four Corners region will drive monsoon moisture northward over California today through Monday, producing plenty of mid- to high-level clouds and even the chance of scattered rain showers and an isolated thunderstorm, primarily on Sunday evening and night.
Temperatures will range between the high 90s and low 100s in the inland valleys, including Paso Robles, while the coastal valleys, such as San Luis Obispo, will reach the low to mid-80s, and most beaches will remain in the mid-to-high 60s. Higher humidity levels from the monsoon moisture will make it feel more uncomfortable.
By the way, Paso Robles finally reached triple-digit temperatures for the first time this year on Thursday when the airport reported a high of 102 degrees.
A cold front will move over our area late Monday night and early Tuesday morning, bringing a deepening marine layer with pockets of mist and drizzle along the coast.
As the cold front moves south of the Central Coast, it will set up a steep pressure gradient, resulting in strong-to-gale-force (25 to 38 mph) northwesterly winds during the afternoon and evening on Tuesday and Wednesday. This synoptic condition will produce low marine stratus clouds at night and in the early morning, with mist and possibly drizzle along the coastline and coastal valleys. Clouds are expected to clear during the late morning and afternoon.
High temperatures at the Mid-State Fair in Paso Robles — which starts on Wednesday — will be in the high 90s to low 100s through Sunday, with temperatures between 101 and 106 degrees the following week. The coastal valleys, such as San Luis Obispo, will reach the low to mid-80s, warming to the high 80s the following week. The beaches will remain in the 60s, except for the southerly-facing beaches of Cayucos, Avila, and Shell Beach, which will hit the low 80s.
More subtropical moisture is forecast to stream over the Central Coast the following week, July 20 through 24, producing higher humidity levels and increasing chances of scattered rain showers and even thunderstorms.
The Climate Prediction Center released its latest El Niño assessment Last Thursday, July 9. It said that El Niño conditions are present in region 3.4, with Equatorial sea surface temperatures (SSTs) above average across the central and eastern Pacific Ocean.
El Niño conditions are expected to strengthen into the Northern Hemisphere during winter 2026-27. The atmospheric circulation anomalies over the equatorial Pacific Ocean are consistent with El Niño.
This winter’s El Niño event has the potential to be one of the strongest on record.
If it verifies, the Central Coast can expect warmer sea surface temperatures, more storms with heavier rainfall, elevated snow levels, and air temperatures well above seasonal averages.
It will also have the potential for more powerful waves from the west or southwest as the storm track shifts southward. Due to thermal expansion of the water column and storm surge, tides can be more than 1- to 2-feet higher than predicted, increasing the risk of coastal flooding.
Surf report
A 3- to 4-foot northwesterly (290-degree deep-water) swell (with an 8- to 11-second period) is forecast along the Central Coast this through Monday.
Increasing northwesterly winds along the central California coastline will generate a 5-to 7-foot northwesterly (300-degree deep-water) sea and swell (with a 5- to 9-second period) on Tuesday through Thursday. This northwesterly sea and swell will lower to 4- to 6-feet (with a 7- to 17-second period) on Friday through next Sunday.
A 1- to 2-foot Southern Hemisphere (205-degree deep-water) swell (with a 14- to 16-second period) is forecast along our coastline on Sunday and Monday, followed by another 1- to 2-foot Southern Hemisphere (225-degree deep-water) swell (with a 16- to 18-second period) on Wednesday through next Sunday.
Seawater temperatures along the immediate coastline will range from 52 to 56 degrees through next Sunday as increasing coastal upwelling brings colder, nutrient-rich water to the ocean surface.
On this date in weather history
1987: Cool air invaded the High Plains Region. Eight cities reported record low temperatures for the date, including Sheridan, WY, with a reading of 37 degrees. Thunderstorms developing along the cold front in the central U.S. produced 6.5 inches of rain at Fort Dodge, IA, and 2.5 inches in one hour at St. Joseph MO. (The National Weather Summary)
2012: High temperatures reached 107-degrees both at Paso Robles Airport and Creston. The maximum temperature at Diablo Canyon only reached 54 degrees, a 53° temperature differential between the coast and the inland valleys.
2017: Former Hurricane Eugene, about 500 miles west of Baja California, is producing a 5- to 7-foot southerly (165-degree, deep-water) swell (with an 11- to 14-second period) along the Southern California coast today. However, this swell is too far southeast to have much effect along the Central Coast.
2017: Paso Robles reached 94 degrees, the first day since July 4 that the temperature didn't hit triple-digits levels.
This week’s temperatures
LOWS AND HIGHS, PASO ROBLES
SUNDAY: 58, 98
MONDAY: 59, 99
TUESDAY: 61, 99
WEDNESDAY: 63, 101
THURSDAY: 61, 99
FRIDAY: 62, 96
SATURDAY: 63, 101
SUNDAY: 67, 100
LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS
SUNDAY: 59, 82
MONDAY: 61, 83
TUESDAY: 61, 84
WEDNESDAY: 63, 87
THURSDAY: 63, 84
FRIDAY: 63, 82
SATURDAY: 66, 84
SUNDAY: 66, 83
John Lindsey is a retired PG&E marine meteorologist. Email him at JohnLindseyLosOsos@gmail.com or follow him on X @PGE_John.