Why is Seattle so much warmer than Vancouver today?

Question

I assume the temperature will not continue to rise, but Seattle is currently 26 degrees Celsius, whereas Vancouver is only 19 degrees Celsius. What is the cause in this huge temperature gap?

Answer 1

Two possibilities.

1. Marine air is being routed over Vancouver. Given the temperature of the Pacific, even a small onshore flow can keep temperatures down during the day. As to why, it could be just the combination of various minor factors that today allow an offshore flow in Seattle. Temperatures can vary widely even between Vancouver Harbor and inland Vancouver for the same reason.

2. A cold front's southern boundary is just north of Seattle.

However I think #1 is more likely. I don't think there are any fronts in that area right now.