Photo courtesy of Philip Tarrant
Photo courtesy of Philip Tarrant

Arizona receives the majority of annual precipitation during two seasons: summer (monsoon season) and winter. Winter precipitation comes from cold fronts and low pressure systems. These systems move south from the Pacific Northwest, often sweeping across Nevada or southern California before bringing cold air and rain or snow into Arizona.

The northern half of the state as well as higher elevations across the state typically receive snowfall in the winter. Northern Arizona receives just over half their annual precipitation in the winter.

The winter storms occasionally extend into southern Arizona, however, southern Arizona receives most of their annual precipitation in the summer. Winter storms rarely bring snow to southern Arizona, but at the highest elevations, like Mount Lemmon in Tucson, snow is not uncommon in the winter.

Arizona’s reservoirs largely rely on winter precipitation to refill.

Arizona Reservoirs

Upper Colorado River Basin Reservoir Levels
Current Colorado River Conditions Dashboard
Salt River Project (SRP) Daily Water Report

Current water levels on Lake Mead and Lake Powell


Excessive Rainfall Outlook

Outlook Day 1 (today)

Outlook Day 2 (tomorrow)

Outlook Day 3 (next day)


Daily Precipitation

Arizona Daily Precipitation


Monthly Precipitation

Arizona Monthly Precipitation


Water Year Precipitation

PRISM WY Precipitation Anomaly


Seasonal Precipitation Colorado River Basin


Snow Water Equivalent

Upper Colorado Basin
Lower Colorado Basin
Little Colorado Basin
Verde Basin
Salt Basin
Gila Basin
State basins


Normal Annual Snowfall

SPC legendSPC legend


Maps display the climate normal data from 1991-2020.

SPC legend
Click on the image to access the interactive map.

  • Arizona Annual Precipitation Map