Heat-driven Northwest drought emergency

The state of Washington declared a drought emergency in May 2015 following a drastic decline in snowpack over the adjoining Cascades. Unlike past droughts that were mainly caused by precipitation deficits, the 2014/15 cold season (November–March) produced near-normal precipitation statewide. In what has since been nicknamed the “snowpack drought” of 2015, this Northwest drought was more a result of unprecedented warmth that caused cold-season precipitation to fall as rain rather than snow on the mountains. A small change in temperature can alter the water balance by reducing the precipitation falling as snow, which results in declined snow water equivalent and summer streamflow.

This type of temperature-driven "snowpack drought" may reoccur due to accelerated anthropogenic warming, according to the fifth edition of "Explaining Extreme Events from a Climate Perspective" by the Bulletin of the American Meteorological Society.[1]

Global warming drives drought through changes in both precipitation and temperatures that vary by region

Depending on a region’s latitude, climate change can reduce or increase the total annual precipitation. It can also concentrate the year’s precipitation into fewer but heavier downpours. This can lead to more runoff and, in turn, contribute to drought. Global warming can also raise local temperatures and drive more frequent and intense heat waves, all of which can dry out land and prompt the early melt of snowpack, another contributor to drought.[2]