Valhalla holds the cold. Air pools behind the Kensico Dam and along the reservoir road, and snow that has already turned to rain a few miles south is still snow up here. Harter Landscaping of Valhalla plows into that pocket — driveways and lots opened, walks and steps cleared, de-icer laid where the wind polishes a surface smooth. Storms in this corner of the county arrive early and leave late, which means heading back out at two in the morning to keep what was already cleared. A drive that stays open the whole storm through is the point, not one that was open once.