PORTLAND, Ore. (KOIN) — Portland and the rest of the Pacific Northwest are currently bewitched by the cool and wet Halloween weather.

It has been a long time coming since we haven’t had measurable rain on Halloween in the last three years. Once we set this aside, there may be more hybrid fall-to-winter days coming our direction.

We are going to start thinking about cool mornings this week. Frost is plausible at this point in time.

Portland is currently sitting at 199 consecutive days of frost-free conditions. The last time we had a temperature that could even be considered in the realm of promoting frost was April 15, when we had a morning temperature of 34 degrees over at the airport. We have to reach back to March 10 for an observation that was below 32 degrees for a freeze (234 days).

With that said, it sounds like our time should be coming soon, right?

On average over the last 30 years, Portland sees a temperature of 36 degrees on November 7. That is one week from today.

Why do we use 36 degrees as a point of contention? Because weather stations are mounted between 4 to 6 feet above the ground. It’s possible that on the surface, those temperatures are even a bit colder. Although the weather station may read 36, there could be frost forming on the grass or plants that are lower to the ground.

November 16 is when we typically see our first 32-degree low for the season. These dates are right around the corner.

We won’t be setting any record-breaking frost dates this season, there have been earlier.


We have another trough dropping south over the region this week. This will bring in a cool pool of air for Wednesday night into Thursday. This is when our temperatures will be coldest this week.

Due to this system right here, we may have afternoon high temperatures in the upper 40s, with overnight temperatures dropping to the 30s! We haven’t had a morning low below 40 degrees since April 24.

There is the potential for locations in the Willamette Valley to drop to the mid-30s — that is cold enough to call for some morning gloves and potentially a heavier jacket. Now weather models are projecting us around that ballpark. There will be cloud coverage in the forecast, which may prevent a significant drop in temperature.

Weather data has been adapting to this projection, boosting our morning temperature a few degrees Thursday morning. Right now, you can see that we are going to be very close to 36 degrees for a lot of locations in the Willamette Valley.

A much colder morning for the higher terrain and central Oregon. Those of you should be prepared for a freeze.

We have yet to drop below 44 degrees this fall. Not only have we been above average for the month, but the morning temperature has also been quite mild recently. The last three days have been warmer in the morning.

If we happen to drop to the mid-30s on Thursday, it will be by far our coldest morning since spring. It might be time to think about dusting off some of the light winter gear too.