The Cascade Mountains will split Washington state into two entirely different weather zones this weekend. In the west, around Seattle, Friday will start with clear skies and temperatures around +27...+29°C, a bit above the usual July norm. But then a weak weather front will move into the region, and by Saturday residents in the western part of the state will see rain—only the second rain on August 1 in the past 40 years. Thermometers will drop to +22°C, though there will be little precipitation, meteorologists say.
The heaviest rain—about a quarter of an inch, or roughly 6 mm—is expected in the so-called convergence zone over Snohomish County. In Seattle itself, the rain will end by Saturday evening, and Sunday will be cool and cloudy, around +22°C. The unsettled weather may force the Blue Angels aviation team to perform their Seafair show flights at lower altitudes. By the way, the westerly wind that brought the front will push smoke from forest fires eastward across the Cascades, keeping the air over Seattle clear.
But for residents of eastern Washington, things will be much tougher this weekend. As soon as the front crosses the mountains, winds on the eastern slopes of the Cascades will strengthen to 30–40 miles per hour. According to meteorologist Dana Felton, this is especially dangerous when fires are already burning. From Saturday through early Sunday morning, extreme fire danger is forecast in eastern Washington, so residents and emergency services need to be as prepared as possible for fire to spread rapidly.
Based on: WA weather: dash of rain in the west, fire-risky winds in the east