By Alex Sosnowski, AccuWeather senior meteorologist
May 24,2017, 3:10:42PM,EDT
Warmer air will return in the northwestern United States during Memorial Day weekend, following a sudden cooldown into Thursday.The flow around a potent storm passing through western Canada is allowing much cooler and more seasonable air to sweep across the region from northwest to southeast during the middle days of the week.
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Temperatures have been slashed by 15 to 25 degrees Fahrenheit from Washington and Oregon to Idaho, Montana, Wyoming and part of Northern California. Highs in the 80s and 90s on Monday were replaced with highs in the 60s and 70s Wednesday. Similar highs are forecast for Thursday.
Strong, gusty winds that accompanied the change to cooler air will settle down by the end of the week.
The midweek cooldown will not set a precedent for the balance of the month. A temperature rebound is forecast for the region prior to the end of the week.
By Friday, highs in Seattle and Portland and Olympia, Oregon, will be in the upper 70s to lower 80s.
Each of the three days of the Memorial Day weekend is likely to feature at least partial sunshine and highs mainly in the 80s. This includes not only Seattle and Portland but also the cities of Spokane and Tacoma, Washington; The Dalles and Pendleton, Oregon; and Boise, Idaho.
Highs from Friday through Monday right along the Oregon and Washington coasts will generally range from the middle 60s to lower 70s.
Rain-free weather will accompany the warmth across much of the region through Memorial Day. Only a few locations across the mountains well east of the Cascades are likely to get a passing thundershower or high country snow shower at midweek.
During the Memorial Day weekend, the weather across the West in general will be ideal for most outdoor plans ranging from honorary gatherings or hiking, attending ball games and fishing.
However, area lakes, streams and the Pacific Ocean are still much too cold for safe swimming. Surf temperatures along the Washington and Oregon coasts range from the upper 40s to the upper 50s. Water temperatures along some streams originating from the Cascades and Rockies are lower.
Attempting to swim in waters this cold can immediately lead to cold water shock, followed by much more dangerous and life-threatening conditions, according to the United States Coast Guard.
Symptoms of cold water shock include gasp reflex, hyperventilation, difficulty holding your breath, rapid heart rate and elevated blood pressure. Following these symptoms, muscle cramps, hypothermia, drowning or cardiac arrest can occur.
Hypothermia can occur in any water temperature below 70, according to the Centers for Disease Control and Prevention (CDC).