What exactly is a Seattle ‘heat wave?’

Residents across the Puget Sound are expected to melt before Sunday &#8212 or at least that’s what it might feel like with temperatures hovering in the low 80s to mid 90s.

The National Weather Service has issued an excessive heat watch across Western Washington from Friday at noon to Sunday at 5 a.m.

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Meteorologist Danny Mercer says the heat wave is coming earlier than usual in the summer and adds to an already hot June.

Is it really a heat wave or are we Pacific Northwesterners sensitive to the giant, yellow orb in the sky?

“A heat wave is all relative to specific areas around the nation,” explained NWS meteorologist Ted Buehner. “For our neck of the woods, when we get into the 90s – heat wave would be appropriate for many people.”

Officially, the National Weather Service defines “heat wave” as “a period of abnormally and uncomfortably hot and unusually humid weather. Typically, a heat wave lasts two or more days.”

Buehner said Seattle averages three days per year in the 90s, not necessarily consecutively. Last year, we had four days reach 90 or hotter.

“It is not rare,” he said, “it just does not happen all that often.

Buehner recalled a “good” heat wave in Aug. 1981. It was during Seafair and temperatures hovered in the 90s for five straight days with two days hitting the then all-time record high of 99.

The forecast says temperatures could hit triple digits east of the Cascade Mountains, as well as parts of Idaho this weekend.