Mark Wysocki, senior lecturer in earth and atmospheric sciences, explains, "So what we have noticed this year is kind of a combination that we have a Pacific Ocean that is a little bit colder than average, which we call a cold pacific or a La Nina. And that tends to force the polar jet stream to move northward into Alaska, and by doing so, that allows the warmer air from the south to penetrate further north. So we end up with this big dome of warm air over the west coast.”