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Background
The San Diego region is known for its mild year-round Mediterranean climate, narrow beaches backed by sea cliffs, inland mountains, and deserts. The complex topography makes it the most biodiverse county in the continental US. Much of its 70 miles of coastline provide recreation and tourism, a key component of the regional economy. The region’s agricultural industry includes many small farms, and San Diego is also a center of high solar power production. The region has many highly populated urban and suburban cities that house its population of ~3.3 million, primarily in the county’s western third.
Extreme Heat
By 2100, temperature is projected to increase substantially by 4 to 9°F under intermediate to high emissions scenarios. Along with average temperature, the number of heat wave days is projected to increase between 20–50 percent with a temperature increase of 6°F. Coastal low clouds are an important part of the region’s climate and can mitigate the impacts of heat, especially near the coast.
Drought and Flood
Precipitation will remain highly variable but will change seasonally, with wetter winters, drier springs, and more frequent and severe droughts. Most models indicate that there will be fewer wet days, but with more intense precipitation. Longer dry, warm seasons with less daytime humidity will cause stronger seasonal dryness of the landscape, and more dry years leading to larger water deficits across the landscape.
Wildfire
The threat of wildfire is projected to worsen with increasingly warm and dry landscapes and longer dry seasons, coupled with occasional dry windy weather patterns. Wildfire risk will increase substantially during dangerous fire weather extremes caused by Santa Ana winds, though projections indicate a mild decrease in Santa Ana Winds in the future.
Sea Level Rise
Sea level along the San Diego County coast is expected to rise approximately 1.6–3.2 feet by 2100, with slim potential for a rise as high as 6.7 feet. For the next several decades, high tides combined with elevated shoreline water levels and large coastal wave events will drive more extreme flooding onshore.