The May 30, 2020 thunderstorm outbreak

What happened

NOAA’s Pendleton office called it a major severe weather event by Northwest standards. A strong upper-level storm crossed the region in the afternoon while the air near the ground was unusually warm and humid for the inland Northwest, with dewpoints in the 60s. With strong winds aloft, storms formed and raced across the region through the afternoon and evening, dropping hail up to 2 inches in central Oregon.

The worst wind hit north-central Oregon. In Wasco County, winds estimated at 100 to 115 mph brought down parts of two high-voltage transmission towers, and riverside camps along the Deschutes River were wrecked. Near Culver and Metolius in Jefferson County a narrow swath of straight-line wind, estimated at 100 mph, snapped power poles, flattened farm buildings and tore roofs from manufactured homes.

The storms moved into southeast and eastern Washington in the late afternoon, gusting 58 to 68 mph at stations in Mattawa, Pullman and Spokane. About 30 power poles came down near Mohler and a dozen fell across Highway 260 near Prescott.

The storm in NOAA’s numbers

NOAA’s Storm Events Database files this storm as 3 episodes from the National Weather Service offices in Spokane (OTX) and Pendleton (PDT), dated May 30, 2020. Counting the six tree-relevant report types (high wind, strong wind, thunderstorm wind, ice storm, winter storm and heavy snow), the episodes hold 38 reports: 1 strong wind and 37 thunderstorm wind (18 in Oregon; 20 in Washington). The same episodes hold 18 other reports (hail 16, flash flood 1, lightning 1), which are not counted in that total. The highest gust among the wind reports is 100 knots (about 115 mph), estimated, in Wasco County, Oregon. Of the counted reports, 16 mention trees in the narrative.

A report is one entry per forecast zone or county per event, so one storm crossing many zones produces many reports. Gusts are in knots as NOAA records them (1 kt is about 1.15 mph).

Affected counties

20 counties have at least one counted report (8 in Oregon; 12 in Washington). The most reports touched Umatilla County, OR (5), Jefferson County, OR (3) and Sherman County, OR (3). Most wind, ice and snow reports are filed by forecast zone, and a zone report is assigned here to every county that zone covers, so a county’s number is the reports that touched it, not separate incidents.

Damage, deaths and injuries

NOAA’s property damage field for these episodes adds up to $203,000 in nominal dollars, as entered by the NWS offices at the time and not adjusted for inflation. Of that, $191,000 is on the counted wind, ice and snow reports and $12,000 on other report types in the same episodes. The event records list 2 deaths (2 direct, 0 indirect) and 4 injuries across these episodes. NOAA’s fatality file gives a location for each death it holds: “Outside/Open Areas” 1; “Boating” 1; “Under Tree” 1.

NOAA entered $203,000 in property damage, all on Spokane office reports; the Pendleton office left the field at zero despite the tower and roof damage it describes, so the real figure was higher. The event records list 2 deaths: the Washtucna cleanup death and a man whose fishing boat capsized in storm-whipped waves on the Snake River. The 4 injuries are on a lightning report near Pasco, and NOAA’s fatality file also attaches one “Outside/Open Areas” row to that lightning report although its event record shows no deaths.

What it meant for trees

Trees are the most common damage in the narratives. NOAA lists trees down in Madras, Boardman, Prosser, Dayton and on Kennewick Avenue in Kennewick, numerous trees and large limbs down in Umatilla County, a 30-foot tree blown over in Crook County, and many large trees uprooted and snapped in the Culver swath. In Davenport more than 40 poplars were uprooted, and in the town of Palouse falling trees damaged homes, a vehicle and a park.

Many yard and windbreak trees east of the Cascades are fast-growing poplars, willows and elms planted for quick shade or shelter. They grow brittle wood, and the Davenport report shows how a windbreak row can go down at once.

What homeowners can learn from it

• Summer storms count. Most storm-tree planning in the Northwest is about winter, but this event and the September 2024 eastern Washington windstorm show that inland areas get damaging thunderstorm wind from May to September. Check large trees near the house in spring.
• Cleanup can kill. A man died during storm cleanup in Washtucna, and NOAA codes the death as “Under Tree”. Leave trees under tension and anything near a line to a crew; see tree work safety.
• Photograph before anything is moved. Pictures of the tree, the stump or root plate and the damage are the evidence an insurer will want; storm damage and tree insurance in Oregon and storm damage and tree insurance in Washington explain what policies usually cover.
• If a tree is on the house, a car or a line, get people out of reach first. Then call the utility for anything touching wires; emergency tree service and fallen tree removal cover what happens next, and tree work safety explains why a crew should handle trees under tension.

Local pages: emergency tree service in Bend, Pendleton and Spokane. Before the next storm season, the tree risk checklist walks you around your own trees, and Oregon storm records and Washington storm records put this storm in context.

How this page was built

Every number above is computed from NOAA’s Storm Events bulk files for episodes 147100, 147114, 148960. Episodes were chosen by ranking all Washington and Oregon episodes from 2016 to mid-2026 on tree-relevant report counts, property damage and tree mentions, and episodes from different offices or states were merged when their narratives describe the same system on the same dates. A same-day high wind report at Summer Lake in Lake County came from a separate system and is left out. Sixteen hail reports in the Oregon episode are not counted. Damage figures are NOAA’s nominal-dollar estimates and are often blank. See all storms on the storm history index and the site’s methodology.