State Climate Summaries: Arizona

Key Messages

Temperatures in Arizona have risen about 2.5°F since the beginning of the 20th century. Recent upward trends in average temperatures and extreme heat are projected to continue. Under a higher emissions pathway, historically unprecedented increases in annual average temperature are projected during this century.

Droughts are a serious threat in this water-scarce state. The potential for more extended droughts in the future will pose a major challenge to Arizona’s environmental, agricultural, and human systems. The risk of very large wildfires is projected to increase.

The summer monsoon rainfall, which provides much-needed water for grazing lands and their ecosystems, varies greatly from year to year. Future trends in average monsoon rainfall are highly uncertain, while high variability is expected to continue. Warmer temperatures may lead to reductions in late-season snowpack accumulation and negative impacts on valley communities that rely on the melting snowpack for summer water supplies.