When Will It Rain?

October 4, 2012

I’ve heard the quote today that the dryness outdoors right now is a “once in a lifetime” experience for this time of year.  That’s not too far off.  Take a look at the driest 3 month periods on record at PDX:

This July-September IS the driest 3 month period ever.  Now we are seeing no rain through at least the first 10 days of October (next Wednesday) and possibly longer.  In 1952, it was drier in May & June.  Remember this year we saw our 2nd wettest June.  In 1967, the autumn rains hit and hit hard the last couple days of September.  October was a soaker.  1991 is quite a good match to this year’s weather with wet May and June, then extremely dry the rest of the warm season.  So we’ve only seen such a combination of dry late summer and a total lack of early Fall rain in 1991 and 1952.  Twice in 70 years; that’s very rare. 

In every other year we see SOME sort of wetting rain at SOME point between late August and early October.  That didn’t happen in those two years and now this year.

So what happened in some of those extremely dry late summers?

1952:  It remained generally dry all the way through November!  BUT, some light rains arrived starting around October 20th.  That would have been the end of any fire danger.

1967:  Already mentioned this above, but after a scorching hot summer and 71 day dry spell (Portland’s longest) it started raining the last few days of September.  October was a big soaker through the whole month, memories of the summer heat and dry weather disappeared quickly.

1991:  Mainly dry until the first cold and wet weather system arrived around the 20th.  I remember this year since I was fresh out of college and it was my first Fall/Winter to forecast.  Snow levels dropped down around 2,000′ the last few days of the month and there was even sticking snow on Halloween up around Boring, Sandy, and the foothills of the Cascades.  Most of the rest of the winter was boring, but that’s another story.

So most likely we’ll see some sort of rain show up during the 2nd half of the month.

Chief Meteorologist Mark Nelsen




So what happened in those other dry