The University of Arizona

Monsoon Summary | CLIMAS

 SW Climate Outlook

Monsoon Summary

Data between June 20-September 17, 2013. Data Source: Western Regional Climate Center

The monsoon is best described by the doggerel “it rained a lot where people are not.” Spatially, much of Arizona and New Mexico received above-average rain. However, the monsoon fizzled over some of the major metropolitan areas in Arizona.

Copious rains fell in the White Mountains of Arizona, the Mogollon Rim area, and around Flagstaff, where precipitation totals have exceeded 10 inches– more than 2 inches above average (Figures 8a–b). In these and other areas, precipitation has been largely above 125 percent of average (Figure 8c). Flagstaff is likely to experience at least the second wettest monsoon on record, and if more rain falls before September 30 – the date the National Weather Service defines as the end of the monsoon – it could rank as the wettest. Southeast Arizona also experienced bountiful rain. July was the wettest on record for Douglas, where more than 10 inches of rain fell. Like Flagstaff, the June15–September 30 period will go in the record books as the second wettest or wettest monsoon. Rain missed many places in the densely populated areas, most notably in Tucson. The NWS rain gauge at the Tucson International Airport has tallied only 3.74 inches through September 15; average monsoon precipitation at this station is about 6 inches. In addition to widespread rain, warmer-than-average temperatures have characterized the 2013 monsoon, particularly minimum temperatures. Tucson, Phoenix, and Flagstaff all had their second warmest monsoon on record. The monsoon was also active in New Mexico, where more than 125 percent of average rain fell in many parts of the state.

The summer storms have helped improve drought conditions. About 90 percent of New Mexico was classified with extreme and exceptional drought conditions on June 18. That number fell to about 6 percent on September 17 (see New Mexico Drought Status). Drought in Arizona also markedly improved. About 30 percent of the state is now classified with severe and extreme drought, down from about 72 percent on June 18 (see Arizona Drought Status).


The continuous color maps (figures at right) are derived by taking measurements at individual meteorological stations and mathematically interpolating (estimating) values between known data points. Interpolation procedures can cause aberrant values in data-sparse regions.

Average refers to the arithmetic mean of annual data from 1971–2000. Percent of average precipitation is calculated by taking the ratio of current to average precipitation and multiplying by 100. Departure from average precipitation is calculated by subtracting the average from the current precipitation.