Timeline: Heavy fall rains, t-storms likely around the PNW

PORTLAND, Ore. (KOIN) — Fall-like rains are taking aim at the Pacific Northwest as wildfires continue to burn across the state of Oregon.

More than a trace of rain is expected with this early-season storm. Tuesday night and much of Wednesday could bring the first real measurable rain to the region this month. This cooler and wetter weather pattern comes less than a week after Portland tied the record for the latest 100-degree temperature in September.

Portland's rain timeline

Rain is expected to fall around the greater Portland, Vancouver metro area just after 11 p.m. Tuesday night. A few bolts of lightning are also possible along the coast with the first few bands of rain Tuesday night. The chance for lightning along the Willamette Valley is possible through the early morning hours Wednesday.

The heaviest of the rain will move through Portland and much of the Willamette Valley from 5-6 a.m. Wednesday. Afternoon heating could make some of these lingering showers bubble up enough to produce an isolated thunderstorm or two later in the afternoon and early evening hours Wednesday.

Rain accumulation remains unclear as weather models range from nearly a half inch to an inch and a half. Forecasts are leaning towards the half-inch mark more closely than the inch and a half. However, nearly an inch and a half is still possible for some isolated locations in western Oregon and southwest Washington.

The return of rain will also help drop temperatures across the region. Afternoon highs will struggle to hit 70 degrees Wednesday afternoon. That's nearly 10 degrees cooler than the average for the first two weeks of September.

This cooler weather pattern will take Portland into the weekend. The chance for rain comes later this weekend and next as this first fall-like rain returns to the Pacific Northwest Wednesday morning.