The first hot spell of the year blows into the Rogue Valley today, bringing with it temperatures that are expected to shoot the mercury up more than 20 degrees above normal for late April and break a slew of records along the way.
The National Weather Service says the heat wave starts today with temperatures in the low 80s around the Rogue Valley, then will spike to 89 degrees Wednesday in Medford before topping out Thursday at a high of 92.
"These next two days will end up the hottest days of the year so far," weather service meteorologist Mike Petrucelli says. "Several locations will be flirting with or breaking records for highs as well."
If Medford hits 89 as forecast Wednesday, that would break that day's record of 86 degrees set in 1981 and scorch the normal high of 69 degrees for late April, according to the weather service. Thursday's forecast of 92 degrees in Medford would tie that day's record set in 1946, according to the service.
Record highs are also expected in Ashland, Brookings and elsewhere in Southern Oregon as winds out of the east will keep marine air not just at bay but well offshore, paving the way for winds to swoop down from higher elevations.
As the air drops it compresses, then warms.
Native Americans along the Umpqua River called these winds chinooks, or "snow eaters," because these springtime effects came as the first chinook salmon of the year headed up the Umpqua.
Similarly, warm air from the Kalmiopsis Wilderness Area in eastern Curry County will blow down the Chetco River drainage from its headwaters, bringing with it temperatures that could push the 80-degree mark Wednesday at the beach.
"In Brookings, we call it the Chetco Effect," Petrucelli says.
While that effect has the Medford forecast at 89 degrees Wednesday, "there might be some areas around the Rogue Valley where it will touch 90," Petrucelli says.
But not in Ashland, where the phenomenon of spring temperatures weighing in at 5 degrees cooler than Medford should hold true.
The weather service forecasts a high of 85 degrees Wednesday and a peak of 88 degrees Thursday. The record high for Ashland is 86 for each of those days, so on Thursday Ashland likely will join Medford in recasting weather ledgers.
"They'll still heat up in Ashland, but not as hot as Medford," Petrucelli says.
The SPF 30 goes back in the glove compartment Friday, when temperatures will fall by 10 degrees Friday and again Saturday, when the mercury is forecast not to cruise above the 70-degree mark — right at Medford's average high for that day.
Reach Mail Tribune reporter Mark Freeman at 541-776-4470, or email at firstname.lastname@example.org.