Historical weather data, all-time temperature records, and monthly climate averages for Sunnyside, WA. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 4th in Sunnyside typically feels like early spring, with an average high of 61° and low of 35°. Across 92 years of records, today has seen a 39-degree spread — from a balmy 77° in 2000 down to a hard freeze at 22° back in 1936. Rain is unlikely, with only a 16% chance of precipitation.
Sunnyside plays in the extremes — the all-time high of 114° on June 30, 2021 ranks among the most intense heat events in Pacific Northwest history, while the record low of -20° in January 1930 shows the valley can freeze hard when Arctic air digs in. Even a single day in 1957 managed to drop 1.7 inches of rain, a remarkable total for a region better known for its dryness.
Sunnyside is a warm, dry corner of Washington, with summer highs routinely climbing into the upper 80s and peaking around 91° in late July. Winters are cold but not brutal — January averages just 38° — and the wettest stretch of the year is the last week of December with only about a third of an inch. If you're chasing sunshine and heat, June through September is your window.