Question: what is the weather like in seattle in mid september?
Answer: Average Weather in September in Seattle Washington, United States. Daily high temperatures decrease by 8°F, from 75°F to 67°F, rarely falling below 59°F or exceeding 83°F. Daily low temperatures decrease by 5°F, from 57°F to 51°F, rarely falling below 45°F or exceeding 61°F.