The Pacific Northwest, meanwhile, offers a different kind of spring: damp, green, and fragrant. In Seattle and Portland, the rain becomes a mist. Cherry trees line the University of Washington quad. And for six glorious weeks, the whole region smells like wet cedar and budding rhododendrons. Locals call it "The Great Thaw" of vitamin D.

In Chicago, spring is a negotiation. One day in March, the temperature might hit 22°C; the next, a sleet storm cancels baseball practice. Midwesterners have a pragmatic relationship with the season. They know better than to pack away the parka. But when the first 15°C day arrives, the city pours into Lakefront Trail—cyclists, rollerbladers, fishermen, and toddlers in puffy jackets eating sand.