Hot, Humid Weather in California

The information here tells how often heat combines with humidity in California cities to create uncomfortably muggy weather.

The apparent temperature, also known as the Heat Index, measures how hot the weather really feels, considering both temperature and humidity. For instance, a temperature of 90 degrees Fahrenheit (32.2 ° Celsius) along with 60 % humidity pushes the apparent temperature to 100 °F (37.8 °C).

At low levels of humidity, high temperatures seem cooler than what the thermometer reads. This often is the case for hot weather in California.

These tables list the number of days when the actual temperature and the apparent temperature rose to least 95, 105 or 115 °F (35, 40.6 or 46.1 °C) for an hour or more. The totals are for the 30 years from 1978 to 2007.

The final table breaks the totals into yearly averages for the days when apparent temperatures reach 95 and 105 °F.

Total days with the temperature at least 95 °F
City Actual Apparent
Fresno 2224 1405
Los Angeles 27 12
Sacramento 1129 683
San Diego 16 13
San Francisco 19 5
Total days with the temperature at least 105 °F
City Actual Apparent
Fresno 265 159
Los Angeles 0 0
Sacramento 65 68
San Diego 1 2
San Francisco 0 0
Total days with the temperature at least 115 °F
City Actual Apparent
Fresno 0 7
Los Angeles 0 0
Sacramento 0 2
San Diego 0 1
San Francisco 0 0
Average days a year of apparent temperature
City 95+ °F 105+ °F
Fresno 47 5
Los Angeles 0 0
Sacramento 23 2
San Diego 0 0
San Francisco 0 0
References

Peter Browning and Brian Walawender. 2009. A Climatology of Apparent Temperature. 21st Conference on Climate Variability and Change.

Back to Top