Weather Blog

Can stormy weekend make this a historically wet September?

Can stormy weekend make this a historically wet September?
Satellite image shows a big storm approaching the Pacific Coast on the morning of Sept. 27, 2013.

Oct. 1 UPDATE: Seattle did indeed set their record for wettest September on record with 6.17" of rain, beating the old record of 5.95"

You probably knew after such a dry July around here that the debt would have to be paid at some point. Looks like September is paying the price... with interest.

Seattle has already doubled its monthly average of September rainfall (1.45") with 3.03" before the rains began Friday in what was promising to be four very soggy days to finish off the month. Two strong cold fronts approaching for the weekend have taped into tropical moisture from old typhoons in Asia and are set to drench much of the Pacific Coast.

Some daily rainfall records for Seattle are in danger of falling: Saturday's is 0.83" and Sunday's is 0.91". But of more note might be getting into among the wettest Septembers on record since we have a good head start. Some forecast models are forecasting over 2-3" of rain for the Puget Sound area by the time we get to early next week, which would put us near or atop the list!

Here are the Top 5 wettest Septembers in Seattle:

1) 5.95 - 1978
2) 5.57 - 1969
3) 4.80 - 2010
4) 4.60 - 1959
5) 4.10 - 1972
...
13) 3.03 - 2013, through Sept. 26.

The storms will also put a nice dollop on our rain year totals, which is measured from October 1 through September 30 to give a better gauge of how an entire fall+winter shaped up instead of resetting in the middle on Jan. 1. So far this year we were already way ahead of normal (remember, last October through December combined was among the wettest on record) at 44.27" heading into Friday. Normal for the year is about 37.5 inches.

We're still quite a ways from a record though, which is 52.84" set in the 1996-97 water year, followed by 50.83 inches in the 1971-72 water year and then 50.42 inches in 1995-96.

Forecasted Rain Map

Just to drive the point home of how wet the weekend is shaping up, here is a forecast chart of 3-day rain totals from Saturday morning through Tuesday morning. The black areas forecast 2.5-5.0" of rain, red is forecasting 5-10 inches and the white spots are over 10" of rain:



Strong winds are possible at times through the weekend, too, especially on the coast and Northwest Interior. The rainy season doesn't officially begin until Oct. 1, but we're apparently starting early this year!