Safeco Field Has a Roof

Safeco Field has the option to be a domed stadium, so you will never have rain falling directly on you from overhead.

Outfield and Upper Deck

Roof Closed
Even with the roof closed, seats in the outfield and upper deck are susceptible to blowing rain

Despite the roof, the sides are open even when the roof is closed. So rain and wind may blow in. To completely avoid the threat of getting wet, avoid all outfield seating and seats in the upper deck.