Excessive Heat — Greater Portland Metro Area, Oregon

2015-06-26 to 2015-06-28 · Greater Portland Metro Area, Oregon

Event narrative

Maximum temperatures were in the mid to upper 90s which is 20 to 25 degrees above the seasonal normals. The low temperatures were in the mid 60s to low 70s. Several new daily temperature records were set for the warmest low temperatures. One man drowned after he fell off a jet ski in the Columbia River on June 27th. This accident occurred around 1 AM, but the warm nighttime temperatures likely contributed to him going into the river at night. The Multnomah County had 10 emergency room visits for heat related illnesses.

Wider weather episode

A strong upper level ridge of high pressure resulted in hot temperatures across Northwest Oregon. Afternoon temperatures peaked in the low 90s to the low 100s which are around 20 degrees warmer than the seasonal normals. Monsoonal moisture and onshore winds resulted in fairly high humidities (40 to 50% in the afternoons) making the temperatures feel 2 to 5 degrees warmer than they were. The mid-level moisture also added to an increase of thunderstorms around the region. Clouds from these thunderstorms limited overnight radiation cooling. Nighttime temperatures were warm with minimum temperatures 10 to 15 degrees warmer than the seasonal normals.

Source: NOAA Storm Events Database, event_id 580563. Narrative written by the NWS forecast office that issued the report.