The weather in Chaco Canyon is inconsistent and unpredictable. Temperatures can fluctuate over 60 degrees during a twenty-four hour period. As with much of New Mexico, precipitation may be localized and one end of the canyon will experience a downpour while the sun blazes and rainbows appear five miles to the east. Due to this irregular weather pattern, reconstructing prehistoric climatic conditions or advising visitors about tomorrow's weather is difficult. Climatic data, such as the chart below, should only be used as a general guide.
The high desert environment of Chaco receives an average annual rainfall of around eight inches. The humidity is very low. Precipitation will frequently evaporate before striking the ground creating virga, the streamers that can be detected below rain clouds. Approximately 36% of the total annual precipitation falls in July, August and September when unstable tropical air from the Gulf of Mexico moves through the Southwest. This moist air produces cumulus clouds and dramatic thunderstorms, enriching the view while bringing much needed moisture to the plants and animals that live here. Throughout the remainder of the year, Pacific and Arctic airstreams dominate Chaco's weather. These systems bring cool temperatures and occasional snow storms.
Temperatures in Chaco rise and fall with the sun. In the summer, days are hot while the nights are cool due to the canyon's elevation of 4175 feet. Frost has appeared in every month except July although it usually occurs from October to May. The yearly variation of temperatures can be extreme with the record high of 106 degrees occurring in July of 1942 and the record low of -38 occurring in December of 1961.
If you are hiking in the canyon, be prepared for heat, rain, wind, and unexpected changes in temperature. Carry extra water, wear sunscreen and a wide-brimmed hat, and if you are going to be out for any length of time, bring along a jacket or sweater. This will ensure your visit to the canyon will not be spoiled by an unpredictable change in weather.