Boo! Halloween brings a full moon and dry forecast


PORTLAND, Ore. (KOIN) – Have you heard that when Halloween comes around in Portland, so does the rain?

It might be your experience that this is the time of the year when conditions start to get rainy. Well, there is no doubt that our average rainfall starts to increase come November. We increase our monthly average to over 5 inches come November.

With all that in mind, we are actually having back-to-back years of dry conditions for Halloween. We actually haven’t had much rain on Halloween since our sloshing back on Oct. 31, 2015. We’ve had a few years with some minor rain, both 2018 and 2016. Take a look at that 2015 year where we nearly topped off at 2 inches of rain.

I happened to be working that day and I have a snap of the radar from the afternoon. The front moving through was pronounced and the atmospheric river was fastened to our region.

That Halloween actually brought in more rain than what we’ve accumulated all month this year. We are almost overdue for another soaker like that.

October, 31, 2015 FILE RADAR IMAGE

Not the case this year. We are actually in store for a real nice forecast. Temperatures topping off in the lower 60s with a clear and dry night. By the evening hours, those temperatures will be down to the 50s with a rather calm wind.

This year may be a bit more tricky because of our ongoing pandemic, but if you’re going to be out and about, you don’t need that rain jacket this year.

We are actually avoiding the rain by a day. A weak system is going to move in on Friday and that is likely going to bring in small measurements of rain. A few weather models try to carry over a drop or two Saturday morning, but it doesn’t look like we have much in the forecast by Saturday.

Right now the forecast is for a dry day, we aren’t anticipating that rain to make an impact on Halloween. If you have anything going on Friday, I would be prepared for some light rain.

Here is a snap of a weather model for Halloween evening. Not only is it going to be dry for us in the Pacific Northwest, but a lot of locations are going to see dry conditions. There is one area of low pressure that looks to bring some rain and snow over the Great Lakes region, but overall dry. There may be a bit of a breeze for southwestern Oregon, but there is really nothing disruptive.

Do you know what else is going on during our Halloween night? We have a full moon! A full moon on Halloween happens roughly every 19 years. However, this is going to the second full moon of the month, which is what is known as a blue moon. The last time we had a blue moon on Halloween, was Oct. 31, 1944.

What would cause the appearance of a blue moon? The moon can also have a bluish color on very cold winter nights when ice crystals in the air form a ring around the moon. The scattering of moonlight by smoke particles can also cause a blue moon. The red end of the spectrum is scattered more than the blue end of the spectrum, which causes light seen from the Moon to look bluer; hence, a blue moon.

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