Does it always rain on Halloween? Looking back at weather records so far this century, the answer to that question is no. Since 2001, it has rained on half the Halloweens in Western Washington, including last Halloween, though it stopped raining by the time the gremlins were claiming their trick or treats.
It also rained on Halloween in 2010, 2009, 2008, 2005, and 2001 at Sea-Tac Airport, and in Olympia and Bellingham.
Some Halloweens have been quite wet. In 1994, at Sea-Tac, the current daily record rainfall of 1.04 inches fell. In 1994, Olympia got 2.94 inches and Hoquiam 2.43 inches. Bellingham had 1.06 inches in 1967.
When it does not rain on Halloween, it sometimes is because high pressure is over the region, resulting in clear skies and quite cool temperatures. For instance, the daily low temperature record at Olympia on Halloween is a raw 14 degrees in 2002. At Sea-Tac Airport, it is 30 degrees in 2006 and at Bellingham, 20 degrees in 1984.
It can be warm on Halloween, too. The record high temperature at Olympia is 74 degrees in 1949 and 71 degrees at Sea-Tac Airport that same year.
This year, we have a weakening Pacific frontal system moving onshore during the day Halloween, bringing some light rain mainly on the coast. A threat of showers will follow this system through Thursday night. Any rainfall should be light amounts, less than a tenth of an inch in much of western Washington. High temperatures on Halloween will register around the daily averages in the middle 50s. Dress appropriately and be safe this Halloween.
For more Halloween historical weather information compiled by Johnny Burg of NWS Seattle, visit www.weather.gov/seattle and look for the Public Information Statement previous version.