Sunday saw record high temperatures for much of southwest Idaho and eastern Oregon. In Boise it got to 91 degrees. That unusual heat brings a chance of thunderstorms for much of this week. But the temperature won’t stay at record levels long. Later in the week highs will likely drop to the 50s.
Jay Briendenbach, the Warning Coordination Meteorologist at NOAA's National Weather Service Office in Boise, says a system of high pressure ridges and troughs is circulating hot and cold air around the country quickly.
“Right now there is a deep trough in the eastern United States. Remember they had the big ridge through a good part of March, record high temperatures; Boston Marathon was close to 90 degrees." He says. "Well the whole pattern has shifted, so now we’re under a ridge and they’re under a trough and actually it’s snowing in portions of New England.”
Breindenbach says climate change is pushing average temperatures gradually up, and the tail end of La Nina is causing some unexpected weather. But for the most part the record high, followed by a steep drop in temperature later this week has a more mundane cause. “It’s spring in Idaho.”
He says wide swings in temperature are the norm for this time of year. And despite Sunday’s record, a high of 90 is fairly common at the end of April in Idaho. But He cautions not to forget swings the other way. Though it’s not in this week’s forecast, Breidenbach says frost is common well into May.