Temperature

Since the Water Year began on October 1, temperatures have generally ranged between 55 and 65 degrees Fahrenheit for the southwestern deserts of Arizona, 35–45 degrees F on the Colorado Plateau of northern Arizona and New Mexico, and 45–55 degrees F in southern New Mexico (Figure 1a). The coldest regions have been in north-central New Mexico’s Sangre de Cristo Mountains where temperatures have dipped to as much as 4 degrees F below average. Elsewhere in Arizona and New Mexico, temperatures have been within 2 degrees F of average (Figure 1b). Near-average conditions seem surprising given that October through mid-December 2012 was an extremely warm period. However, in recent weeks, temperatures have nosedived. Starting in mid-December, a series of cold low-pressure systems moved through the western U.S., with several bringing cold air to the Southwest. Most notably, in the second week of January a looping jet stream delivered Arctic air to the Southwest, and freeze warnings were issued by the National Weather Service for four mornings in a row in the Phoenix area and other regions across the Southwest. This was the longest cold snap since December 1978.  Record low daytime and nighttime temperatures were recorded in the southwestern deserts. As a result, temperatures over most areas of both states during this four-day period beginning on January 11, were 4 to 12 degrees F below average, with only southeastern New Mexico escaping the bitter cold at a mere 0 to 4 degrees colder than average (Figures 1c–d).