Air temperatures have increased over the past century, driven mainly by changes in nighttime temperatures.

One of the most definitive indicators of climate change is air temperature. The rise in global air temperatures is linked to increased concentrations of carbon dioxide and other greenhouse gases from human activities in the Earth’s atmosphere. Warming air temperatures impact the weather, the water cycle, human health and well-being, and ecosystems. For more information, download the Air Temperatures chapter.

What does this indicator show?

Statewide annual average air temperatures

This line graph shows the annual average air temperatures (°F) from 1895 to 2021 in the grey dotted line and the 11-year running average in the solid red line.

• Statewide annual mean temperatures have increased by about 2.5 degrees Fahrenheit (°F) since 1895. Warming has accelerated, and seven of the past eight years have been the warmest on record. 

• Some of the warmest years coincided with some of the driest years, leading to exacerbated drought conditions. Droughts of the 21st century have been hotter, longer lasting, and more widespread than before. 

• A warming climate has far-reaching effects on our health, well-being, ecosystems, and natural resources.   

• Extreme heat, poor air quality, droughts, and other severe impacts of warming temperatures disproportionately fall on underserved communities. These communities are least able to prepare for and recover from such impacts. 

• Carbon dioxide and other greenhouse gases have driven unprecedented warming worldwide. 

• Temperatures are also influenced by the natural landscape, elevation, proximity to the ocean, and atmospheric and oceanic circulations. 

• Changes in land use and land surface exert local effects on temperature. For example, heat-absorbing concrete and asphalt in buildings and roads have a warming effect, and irrigation has a cooling effect. 

• CalAdapt, Annual Averages
• Calfornia Energy Comission, Governor's Office of Planning and Research and Natural Resources Agency, California's Fourth Climate Change Assessment​
• National Oceanic and Atmospheric Administration, California State Climate Summary 2022
• National Oceanic and Atmospheric Administration, Climate at a Glance
• National Oceanic and Atmospheric Administration, Storm Events Database
• Western Regional Climate Center, State Climate Trackers
• Oregon State University, PRISM Climate Group
• University of Oxford, Global Warming Index