2A: Long-term trends of Utah’s climate

Analysis of historical Utah climate data shows that since 1950, nine months of the year have had declines in total precipitation, with the greatest drying in the crucial months from March through August^[1]. Over that same period, temperatures have warmed in all months but October. 

Most of Utah’s water supply is delivered as snow that accumulates during the winter and early spring. January through March historically are the most productive snow accumulation months, and since 1950, this period has seen a slight dip in total precipitation (Figure 2A.1). There is also a trending decline in low-pressure troughs passing over the state and bringing precipitation, increasing deficits of soil moisture. In addition, as temperatures have warmed (Figure 2A.2), the typical snow accumulation months from November to May are receiving more frequent rainfall (Figure 2A.3). 

Implications of increasingly rain-driven winters are primarily negative because snowpack that holds water is diminished. More rain stresses Utah’s warm-season water supplies used for agriculture, recreation, municipal water, and industry. These wintertime trends have accelerated in recent decades in Utah’s low and mid-elevations, further stressing the state’s water supply.