Cliff Mass: Fourth of July weather — the facts

There is a lot of weather mythology about the Fourth of July in the Northwest.  Some believe it always rains or that the weather is worse than other nearby days.  Or that the fireworks “seed” the atmosphere for more clouds for particularly poor weather late on the fourth.

There ARE some interesting climatological aspects of this weekend…so let’s check it out. Here is a plot of the climatological probability of measure precipitation at Sea-Tac Airport.

You  can see that during the latter part of June we are locked into roughly a 27% chance of rain and that this value holds into the July 4th weekend.   But then the Northwest magic occurs. (more)



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