The clouds were the first giveaway. Nine days into a freezing start to February, the first of a warm series of four 45-plus degree days sported a few puffy, springlike clouds laced across an azure sky.

After two below-zero mornings and four days when the highs failed to reach freezing, these beacons of spring spelled joy. The aging black lab frisked around a greening Fellin Park, the first daffodil stems stretched upward, and early afternoon walkers smiled as they passed. Winter’s harshest weat...