Key Takeaways:

• Climate extremes, like severe daytime highs and heavy rainfall, have not increased since 1900.
• The number of extremely hot days per year is comparable to the 1930s, average warming has been driven by the urban heat island effect producing warmer nights.
• There has been no long-term trend in average precipitation since 1900, major droughts are within historical norms.
• There has been no increase in wildfire number or size in recent decades.
• Major crops like almonds, strawberries, and grapes are not experiencing negative impacts from climate change.

Short Summary:

Temperature Trends:

California is one of the most ecologically and climate-diverse regions in the world, containing mountains, deserts, and even rainforests. The state has more than 800 miles of coastline along the Pacific Ocean, which greatly influences weather patterns. In the south, the state is dominated by deserts where temperatures regularly exceed 100°F, with much of the region getting little rainfall. Coastal regions see what Köppen classification calls a Mediterranean climate, with most rainfall in the winter months and temperatures remaining moderate year-round.¹⁵ In the northern parts of the state, there is more humidity and rainfall, enough that redwood forests in coastal California are classified as temperate rainforests.

The average temperature in California has risen approximately 3°F since 1900.² However, the number of “extremely hot” days, or days where maximum temperatures are 100°F or above, are comparable to the 1930s. The slight increase in average temperature is almost entirely driven by warmer nighttime temperatures, particularly fewer very cold nights.³

Part of the nighttime warming is due to the Urban Heat Island (UHI) effect, which is driven by the growth of urban sprawl, especially land use changes and increasing hard surfaces like asphalt and concrete.⁴ California saw its population climb from 1.4 million residents in 1900 to nearly 40 million in 2025. Los Angeles has grown from a population of around 100,000 in 1900 to 3.89 million today, and San Francisco’s population has doubled during that period. Cities like Los Angeles and San Francisco have seen more temperature rise than rural areas, which points towards UHI as a major driver of local warming due to the increase in population.⁵

Precipitation

There has been little overall change in the average yearly precipitation in California since 1900. There has been a slight decline in very recent decades, but no long-term pattern overall, and no increase in what would be considered “extreme” precipitation events.⁶

Drought is a major and recurring hazard for California, especially in the southern part of the state, exacerbated by increased water use for agriculture in the desert and population growth. Recent dry periods are within the historical norms.⁷

State-Specific Issues:

Wildfires

Wildfire has always been a serious risk across California, and is a natural part of the landscape, especially during dry seasons. Data from the National Interagency Coordination Center show that, outside of a particularly bad fire season in 2020, wildfire counts and burned acreage have been stable over the period of record.⁸

Going back further, research published in the journal Forest Ecology and Management reported that prior to European colonization in the 1800s, more than 4.4 million acres of California forest and shrub-land burned annually.⁹ And those huge wildfires came when the earth was cooler than today.

Sea Level Rise

California has 16 sea-level monitoring sites along its coastline, the most of any single state. Relative sea level trends vary from a rise of 5.08 mm (0.2 in) per year at the North Spit monitoring station, to falling levels of -0.76 mm (-0.03 in) per year at the Crescent City station.¹⁰

The sea level fall in Crescent City is due primarily to tectonic uplift. In contrast, the nearby Humboldt Bay, which contains the North Spit station, is sinking also because of tectonics, but tectonic subsidence rather than uplift. This increases the rate of relative sea level rise tremendously.¹¹

California’s entire coastline is tectonically active, which impacts relative sea level rise regardless of climate change.

Agriculture:

California’s agricultural sector is dominated by almonds, which California exclusively produces in industrial quantities in the United States, as well as grapes and strawberries.

The amount of land devoted to almonds rapidly grew throughout the 2000s, and production trends reflect that, increasing 633 percent since 1995, with yields increasing 122 percent over that same period.¹²

Grapes are also important to California, famously for both wine and foods like fresh grapes and raisins. Since 1998, grape production has decreased, driven largely by crashing prices and a significant decline in demand for wine.^13,14

Strawberry production has risen 104 percent since 1998, and yields improved by approximately 9 percent during the same period.¹⁵

Conclusion:

California is not suffering dangerously from climate change. Warmer temperatures are largely due to increased urban development. Recent droughts trends are within their historical range. And there has been no notable increase in wildfires in recent decades. Major crops like almonds are doing very well, despite their high-water demand.

References:

1. 1. “United States Koppen-Geiger Climate Classification Map,” plantmaps.com, January 20, 2024, https://www.plantmaps.com/koppen-climate-classification-map-united-states.php#google_vignette
   2. “California State Climate Summary 2022,” National Oceanic and Atmospheric Administration, https://statesummaries.ncics.org/chapter/ca/
   3. Ibid.
   4. “Urban heat islands,” The Heartland Institute, Climate at a Glance, https://climateataglance.com/climate-at-a-glance-urban-heat-islands/
   5. “California Temperatures on the Rise,” NASA Earth Observatory, April 17, 2007, https://science.nasa.gov/earth/earth-observatory/california-temperatures-on-the-rise-7596/
   6. NOAA National Centers for Environmental Information, “Statewide Time Series,” Climate at a Glance, accessed June 16, 2026, https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/4/pcp/12/1/1900-2026
   7. “California State Climate Summary 2022,” National Oceanic and Atmospheric Administration,
      https://statesummaries.ncics.org/chapter/ca/
   8. “Intelligence: NICC Annual Reports,” National Interagency Fire Center, accessed June 15, 2026, https://www.nifc.gov/nicc/predictive-services/intelligence
   9. “Prehistoric Fire Area and Emissions from California’s Forests, Woodlands, Shrublands, and Grasslands,” Forest Ecology and Management, https://doi.org/10.1016/j.foreco.2007.06.005
   10. NOAA Center for Operational Oceanographic Products and Services, “Relative Sea Level Trends — North Pacific Station Trends,” National Oceanic and Atmospheric Administration, accessed June 16, 2026, https://tidesandcurrents.noaa.gov/sltrends/regionalcomparison.html?region=USNP
   11. “Tectonic Land Level Changes and Their Contribution to Sea-Level Rise, Humboldt Bay Region, Northern California,” Cal Poly Humboldt Sea Level Rise Institute, 2017, https://digitalcommons.humboldt.edu/hsuslri_local/23
   12. USDA National Agricultural Statistics Service, “California Almond Production and Yield (utilized, shelled), 1995-2025,” NASS Quick Stats database, accessed June 16, 2026, https://quickstats.nass.usda.gov/results/72344DA2-72AE-386D-8813-A34DA52273AE
   13. USDA National Agricultural Statistics Service, “California Grape Production and Yield, 1998-2025,” NASS Quick Stats database, accessed June 16, 2026, https://quickstats.nass.usda.gov/results/3F60C076-175A-346A-B89E-4ECDC8400EE0
   14. “California’s Wine Grape Crush Hits a 26-Year Low,” The Grape Reset, May 3, 2026, https://thegrapereset.com/blog/californias-wine-grape-crush-hits-26-year-low
   15. USDA National Agricultural Statistics Service, “California Strawberry Production and Yield, 1998-2025,” NASS Quick Stats database, accessed June 16, 2026, https://quickstats.nass.usda.gov/results/597FCB1D-1056-3D55-81D9-E8279DA13716

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