What is this mile usually like?
Forecasts say what the road will do tomorrow. This page says what it usually does — freezing hours, snow, freezing rain, black-ice nights, truck-tipping crosswinds and low-sun glare for every week of the year, computed at 5,580 road nodes from fifteen winters of ECMWF ERA5 reanalysis and the geometry of the roads themselves. Nobody publishes this. Now it's published.
The National Boards
Superlative Miles · AnnualizedSeasonal Risk, Route by Route
52 Weeks × 8 HazardsHow It's Built
Method · Honest UnitsECMWF's ERA5 reanalysis (via Google's public ARCO archive, 0.25°, 3-hourly samples) is read at the nearest gridpoint to each road node: Nov–Mar over 15 winters (2010–2025) for the cold-season statistics, Apr–Oct over five recent years for the warm season. Snow and freezing-rain hours use ERA5's own precipitation-type diagnosis. Crosswind hours are the wind component perpendicular to the local road bearing above 25 kt — the bearings come from our own route geometry. Sun-glare hours are pure astronomy: the sun within 12° of the road axis while 0–8° above the horizon. Black-ice nights are counted sequences — a wet afternoon, then a calm, dry night that falls through freezing. All values are per-week normals; a 0.25° gridpoint smooths the sharpest passes, so treat pass-top values as floors, not ceilings.