Pressure does affect salmon but who cares, you are out there and will fish anyways in hopes that one of them does not care either!

Pressure may affect Steelhead but temperature has way more affect than pressure. How many times have you fished all morning without a bite and then catch fish from 10:00am to 2:00pm or whenever the bite stops? Most of the time the water temp will rise by mid morning, just enough to turn them on, but again, who cares, you are there and fishing so you just keep chucking gear waiting for the bite!