The most serious threats to the public health of Californians will stem primarily from the higher frequency of extreme conditions, principally more frequent, more intense, and longer heat waves. An increase in heat waves may increase the risk of directly related conditions such as heat stroke and dehydration.
Simply click on an area of interest on the map or enter an address in the search bar above. You will see the first of six different charts that display different aspects of projected extreme heat events. Each chart is accompanied by a brief description below the tool. Note that you can view the results of both “high” (A2) and “low” (B1) emissions scenarios showing different projected outcomes based on varying assumptions.
What is an extreme heat day?
For the purposes of this tool, an extreme heat day is defined as a day in April through October where the maximum temperature (Tmax) exceeds the 98th historical percentile of maximum temperatures based on daily temperature data between 1961-1990. A heat wave is defined as 5 or more consecutive extreme heat days.
About the Data
The data being displayed in this tool have been provided by Scripps Institution of Oceanography. The data are the results of modeled simulations, consisting of historical model simulations for 1950-1999 and climate change projections for 2000-2099 using the GFDL CM2.1 Global Climate Model. Note that model data do not represent actual “observed” values for the historical time period, but rather are coupled model simulations that are run over the historical period. Thus, the simulations include both a retrospective historical period and the 21st Century projected climate run which is driven by a scenario of hypothetical greenhouse gas emissions. Climatologists compare statistics of the model data for the historical period to gage the model’s ability to simulation recent climate and climate variability. The relative differences between its projected climate and a model’s historical climate is used to determine characteristics of possible climate change, including timing, magnitude, pattern and rates.
The data presented in this tool represent a projection of potential future climate scenarios, they are not predictions. These data are meant to illustrate how the climate may change based on a variety of different potential social and economic factors. The default visualizations in this tool are comprised of the average values from a variety of scenarios and models. Find out more about climate change data.
This information is being made available for informational purposes only. Users of this information agree by their use to hold blameless the State of California, and its respective officers, employees, agents, contractors, and subcontractors for any liability associated with its use in any form.
This work shall not be used to assess actual coastal hazards, insurance requirements, or property values and specifically shall not be used in lieu of Flood Insurance Studies and Flood Insurance Rate Maps issued by the Federal Emergency Management Agency (FEMA).