SeaTac experiences a classic Mediterranean-influenced oceanic climate, classified as Köppen Csb, typical of the Pacific Northwest.
Summers are generally warm, dry, and sunny, with average high temperatures in July and August reaching the mid-to-upper 70s (°F) and occasionally breaking into the 80s or 90s. Winters are cool, wet, and overcast, with average lows hovering around 37°F and highs in the upper 40s.
The city averages about 39 inches of rain per year, falling predominantly between October and April. Snowfall is relatively rare and usually light, averaging a few inches per year, though occasional winter storms can bring heavier accumulations. The best time to visit is from July through September, when the weather is consistently dry and pleasant.