You'll likely spend much of your trip indoors, but if you're planning to venture beyond the casino, looking at local weather trends is a good idea. The hottest months are usually August and July, with an average temperature of 17°C, while the coldest months are February and December, with an average of 5°C. The rainiest months in Mukilteo are November, January, December and October, with each month seeing an average of 226 mm of rainfall.