When the barametric pressure is falling is when it turns on, until the low passes, then as it rises the fish become less active. When the barametric pressure is holding steady expect the usual. Just before a low comes through can be tremendous. I've had days on fall chinook where it was so slow trolling was wasting gas, then a system began to move in, fished just before the low and it was craziness....seemed like everyone had 1 on in every boat.