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Published March 21, 2012
Precipitation(data through 3/14/12)
Data Source(s): High Plains Regional Climate Center
Precipitation since the water year began on October 1 generally has been between 50 and 70 percent of average in Arizona and southern and eastern counties of New Mexico (Figures 2a–b). Maricopa and Mohave counties and northern Apache County have been particularly dry, measuring less than 50 percent of average. Most of Southern California also has seen scant rain and snow. The cause of the dry weather in Arizona and California has been the position of the storm track. Generally, storms have either moved south into Mexico before wafting northeast through New Mexico, or they have tracked through Nevada and Utah before dropping down into New Mexico. Both of these trajectories have been a boon to northern and central New Mexico, however, as precipitation there has been between 100 and 300 percent of average.
In the past 30 days, only two winter storms passed through Arizona. The first dumped precipitation across the northern counties in Arizona and northwestern New Mexico, while the other wafted south into Mexico, dropping precipitation on the southeast corner of Arizona and the southwest corner of New Mexico. Most of the Southwest experienced precipitation totaling less than 75 percent of average, but several areas received well-above average rain and snow. The high variability in the past month—from 2 percent of average in many areas to more than 400 percent of average in others—is not unusual during La Niña winters. La Niña events tend to bring drier, more variable conditions, while El Niño events often more consistently deliver wet conditions.
The water year begins on October 1 and ends on September 30 of the following year. As of October 1, 2011, we are in the 2012 water year. The water year is a more hydrologically sound measure of climate and hydrological activity than is the standard calendar year.
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.
The continuous color maps (Figures 2a, 2c) 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.
The dots in Figures 2b and 2d show data values for individual meteorological stations.
For these and other precipitation maps, visit:
For National Climatic Data Center monthly precipitation and drought reports for Arizona, New Mexico, and the Southwest region, visit :
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Dan Ferguson, CLIMAS Program Director
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, CLIMAS Associate Staff Scientist
- Gigi Owen, CLIMAS Assistant Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Swetish, CLIMAS Publications Assistant
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
The CLIMAS Web site contains official and non-official forecasts, as well as other information. While we make every effort to verify this information, please understand that we do not warrant the accuracy of any of these materials.... Read full disclaimer