September 8, 2025

San Diego to Experience Significant Cooling Trend

News Summary

San Diego is set to experience a significant cooling trend this week as a marine layer returns, dropping temperatures across the region just weeks before autumn. The National Weather Service forecasts daytime highs of 74°F on Tuesday, decreasing to 71°F by Thursday. While inland areas like Escondido will see a similar dip, the cooling trend will not bring significant rainfall, with a drier than normal fall expected due to La Niña. The forecast also highlights windy conditions and temperature fluctuations as the week progresses.

San Diego is set to experience a significant cooling trend this week, as a thick marine layer returns to the area, bringing cooler and more seasonal temperatures just two weeks before the official start of autumn. According to forecasts from the National Weather Service, daytime high temperatures in San Diego are expected to range from a high of 74°F on Tuesday, decreasing to 71°F on Thursday, before slightly rising to 73°F on Friday. In contrast, the seasonal average temperature for the region typically hovers around 78°F.

This marine layer is predicted to affect various parts of the county, including inland foothills and valleys, where temperatures in areas like Escondido will also see a notable dip. The forecast for Escondido shows highs of 80°F on Tuesday, dropping to 76°F on Wednesday and Thursday, and recovering to 79°F on Friday.

Additionally, the water temperature off the coast is currently between 70°F and 73°F and is expected to decrease as the cooling trend sets in. However, San Diego County should not rely on this temperature shift for significant rainfall. The 10-day forecast does not predict any major storms, meaning rain relief is unlikely. To date, San Diego International Airport has recorded only 4.61 inches of precipitation since the start of the water year on October 1, which is more than five inches below the average for this time of year. The water year concludes on September 30.

Looking ahead, forecasters from NOAA suggest that Southern California may experience a drier than normal fall due to the development of a La Niña phenomenon. High pressure building over the Southwest is expected to compress this marine layer, which will limit cloud cover by midweek, resulting in temperature fluctuations.

On Monday, conditions will be slightly warmer before the cooling trend sets in. The forecast indicates that coastal temperatures will range from 69°F to 74°F, while inland areas are expected to experience highs of 75°F to 79°F. Western valleys could reach between 78°F and 82°F, and foothills will see temperatures range from 85°F to 90°F. The mountains are predicted to have highs between 84°F and 92°F, while desert regions could encounter extreme temperatures from 103°F to 107°F.

As the week progresses, temperatures are expected to rise significantly from Thursday through Saturday, particularly in the desert areas, where highs may exceed 110°F. During this period, monsoonal moisture is forecasted to sweep into the region, increasing the likelihood of showers and thunderstorms, especially in mountain and desert areas. The chances for storms will peak on Friday and Saturday and could extend into the evening hours, bringing needed moisture to the region.

Windy conditions will also materialize midweek, particularly in mountainous and desert areas, with gusts potentially reaching between 25 to 45 mph. By Wednesday, daytime highs are expected to return to seasonal norms, before climbing above average temperatures through the weekend.

This week’s unusual weather fluctuations highlight the diverse climate patterns of San Diego County, marked by both cooling trends and the potential for monsoonal moisture, while still pointing to an overall persistent drought situation.

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Additional Resources

Author: STAFF HERE SAN DIEGO WRITER

SAN DIEGO STAFF WRITER The SAN DIEGO STAFF WRITER represents the experienced team at HERESanDiego.com, your go-to source for actionable local news and information in San Diego, San Diego County, and beyond. Specializing in "news you can use," we cover essential topics like product reviews for personal and business needs, local business directories, politics, real estate trends, neighborhood insights, and state news affecting the area—with deep expertise drawn from years of dedicated reporting and strong community input, including local press releases and business updates. We deliver top reporting on high-value events such as Comic-Con International, San Diego County Fair, and San Diego Pride Festival. Our coverage extends to key organizations like the San Diego Regional Chamber of Commerce and United Way of San Diego County, plus leading businesses in biotechnology, healthcare, and technology that power the local economy such as Qualcomm, Illumina, and Scripps Health. As part of the broader HERE network, including HEREAnaheim.com, HEREBeverlyHills.com, HERECostaMesa.com, HERECoronado.com, HEREHollywood.com, HEREHuntingtonBeach.com, HERELongBeach.com, HERELosAngeles.com, HEREMissionViejo.com, and HERESantaAna.com, we provide comprehensive, credible insights into California's dynamic landscape.

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