Climate Variation at Flagstaff, Arizona 1950 to 2007

Flagstaff is becoming warmer and drier. Estimated average-daily temperatures of the Flagstaff area are 2.3-degrees warmer since 1970 and annual precipitation at Flagstaff has been below average for nine of 11 years since 1996. Rising temperatures in the area parallel those of global-surface temperatures, particularly the rapid rise since the early 1970s.

Ongoing drought since 1996 is strongly affecting winter, spring, and fall precipitation. Winter moisture has been below average in 11 of the past 12 years, spring was below average in eight of the past 11 years, while fall was below normal in nine of the past 12 years. The precipitation decrease of the three seasons is 44 percent since 1996. In contrast, summer-monsoon related rainfall is unaffected by the ongoing drought. Although summer rainfall tends to be more abundant and dependable than the other seasons, cool season moisture is more important hydrologically. This means that aspects of Flagstaff's environment that require cool-season moisture, particularly the ponderosa pine forest, are increasingly stressed.

[Summary provided by the USGS.]