PORTLAND, Ore. (KOIN) — Heavy mountain snow, below normal temperatures and the return of rain falls over parts of the Pacific Northwest this week.

The biggest winter impacts of the week will be felt over the Cascades where snow elevations are expected to fall to nearly 2,500 ft. by mid-week.

Parts of the Willamette Valley and most of Portland will feel the first signs of winter with a major temperature drop later this week. Afternoon highs will fall to the low 50s with even colder early morning lows.

Daytime highs will sit nearly five to 10 degrees cooler than the normal average daytime high temperatures by the middle of the week. Early morning lows will fall even closer to freezing with the mercury only expected to sit in the mid-30s by the weekend. This might feel like a shock to the system as Portland hasn’t seen morning lows in the 30s since April 20, 2023.

KOIN 6 Meteorologist Josh Cozart shares the number of days it’s been since Portland’s seen early morning lows in the 30s

That means Portland hasn’t seen temperatures this cold in over 186 days. April 20 was when early morning lows dipped to 37°F and much of the Pacific Northwest could fall even colder than that this weekend.

Patchy frost is possible for some this week as skies begin to clear and cooler air moves in by the middle of the week.

Typically, Portland doesn’t see its first average freeze until November 12. That average isn’t expected to be surpassed this week as temperature forecasts keep the mercury in the mid-30s through the weekend.

Portland’s average first freeze and earliest first freeze of autumn observed from the years of 1940-2021

The earliest first freeze of the season was recorded on October 8, 1985. For closer comparison, Portland saw its first freezing temperature last year on November 13, 2022.