Sunday in Oregon: Rain arrives for 1st major fall storm

PORTLAND, Ore. (KOIN) -- A pause in the rain Sunday morning is short-lived as more widespread and persistent rain returns to the Pacific Northwest by Sunday afternoon.

Cloudy skies will remain over western Oregon and Washington Sunday morning as some of the strongest seasonal rains in months return to the region. The morning cloud coverage and afternoon rain will keep temperatures mild. Highs will only make it into the mid- to upper-60s Sunday afternoon and evening. That puts Portland nearly 10 degrees cooler than normal for the final week of September.

Track Portland's rain with the most accurate KOIN 6 radar

Rain accumulation will really start to increase later in the day. Showers will start falling over the Portland area around noon and will continue into the start of next week. Some thunderstorm activity is possible farther to the west late Sunday night. The best chance to hear thunder or see lightning Sunday night is along the coast and over the coast range.

That thunderstorm potential remains through Tuesday for much of western Oregon and Washington. No severe weather is expected, but a bolt of lightning and a rumble of thunder is possible for some next week.

Flooding and strong winds are possible in the southwest corner of Oregon Sunday night through Monday. The flooding threat increases as heavy rain falls over recently burned areas west of Medford. Strong winds are also possible east of Medford Monday.

Rain accumulation will continue to add up from Sunday to Wednesday. Rainfall totals could help Portland surpasses the average monthly rainfall totals for September by nearly a half-inch.

That would help improve the extreme drought conditions that have worked their way back into Oregon and Washington's mountainous areas.

Cooler and wetter weather than normal will stay over Portland through the end of next week. Drier and eventually sunnier skies aren't expected to return until next weekend.