Western Regional Climate Center


May in the West

Winter continued its grip throughout the west in May with numerous cold fronts leading to cool and blustery weather for the month.

Temperatures were below normal for the western U.S. except for a small portion of New Mexico. Some locations reported average monthly temperatures 8-10 degrees below normal for May. In Lander, WY, it was the coolest May since 1950 and the coolest in Ely, NV, since 1953.

Although numerous cold fronts blew through the west, precipitation was mostly below normal except for pockets of the Pacific Northwest, California and eastern Montana. It was the second wettest May in Yakima, WA, and the wettest since 1948.

Thanks to cool, cloudy and occasional snowfall throughout April and May in the Sierra Nevada of California the percent of normal snow water equivalent increased from 90% on April 1 to 120% on May 1 to roughly 150% on June 1. Snow melt was delayed throughout the rest of the west as well with percent of snow water equivalents increasing from 50% on May 1st to over 100% in the Pacific Northwest and northern Rockies by the end of the month.

Significant Events for May 2010

May 3: Strong frontal winds in Pacific Northwest: A powerful front kicked up strong winds throughout the Pacific Northwest causing widespread local damage to trees and power lines. Numerous accidents were reported with blowing dust, reducing visibility to less than 100 feet in some locations. Blowing dust caused a couple of accidents on Interstate 84 in the Hermiston, OR, area.

May 18: Tornado in Laramie County, WY: An EF-2 tornado hit Burns, WY, (30 miles east of Cheyenne) on the evening of the 18th. One house lost its roof and several outbuildings were destroyed. This same storm produced golf ball sized hail that accumulated to a depth of up to 3 feet in some locations and severe flash flooding.

May 19: Severe weather in Pacific Northwest: Another strong front produced an EF0 tornado near Moses Lake, WA, damaging a barn and grain silo. This same storm blew down six large pine trees near Hayden Lake, ID, causing significant damage to a home and injuring one person. Three other homes in the area were also hit by falling trees. In Moscow, ID, thunderstorm winds ripped the roof off the La Quinta Inn injuring one person. A funnel cloud was spotted just prior to the event.

May 24: Damaging winds in Colorado: Three semi-trucks and an RV were blown over in a 10-mile stretch of Interstate 70 near Limon from strong frontal winds in the early afternoon of the 24th. Winds were reported as gusting up to 70 mph. Numerous flights were cancelled and delayed at Denver International Airport as winds gusted to 61 mph. In Colorado Springs at least eight soldiers were injured during a Fort Carson training session when the winds blew a tent off the ground.

May 26: Damaging Hail in Colorado: Hail up to 3 inches in diameter tore leaves from trees and destroyed numerous car windows in the Denver metro area.

May 2010 Departure from Normal Temperature and Percent of Normal Precipitation for Western United States

Departure from normal temperature Departure from normal precipitation

© Western Regional Climate Center