Wind chill: the cold you actually feel
At speed, the air temperature on the forecast is not what reaches you. Using the standard wind-chill formula, 5 °C at 100 km/h feels like about −3 °C on exposed skin, and 10 °C feels like about 4 °C. That is why a ride that is pleasant in town becomes a numb-fingered slog on the motorway.
Good kit moves this limit a long way. Heated grips, a heated vest, a proper winter glove and a scarf or neck tube that closes the gap at the collar turn a miserable 5 °C ride into a comfortable one. Cold hands are also slow hands, which is a safety problem, not only a comfort one.
Cold roads have less grip, even when dry
Tyres are built to work warm. On a cold road the rubber never reaches its working temperature, so a dry road in November simply has less grip than the same road in July — and it looks exactly the same. Riders underestimate this precisely because nothing looks wrong.
Take the first corners gently, expect the tyres to warm up slowly or not at all on a cold day, and leave more margin on shaded roads, bridges and anything that stays out of the sun.
Ice is the real limit
The hard stop is ice, and it needs two things together: a surface at or near freezing and moisture on it. A cold, dry road is ridable with care; a cold road after rain, or with frost, is not. Bridges, shaded bends and hollows freeze first and thaw last, so they can be icy while the forecast for the area reads a few degrees above zero.
RideWindow vetoes an hour outright — it scores 0, No-Go — when the air is below 2 °C and it has rained in the last two hours, and when its grip estimate finds a wet road at or below freezing. No preference setting overrides either rule.
How RideWindow scores cold
By default the ride score treats 8–32 °C as the comfortable range: the temperature points are highest in the middle of it and fall away quickly below or above it. You can set your own range in a free rider profile, so a rider with heated kit is not marked down for a crisp morning. The grip estimate is separate: it prices the cold road no matter what your comfort range is, because tyres do not care how warm your jacket is.
To see how cold the coming week is where you ride, search your town, or check a mountain pass on the cities and passes page — air cools by roughly 6.5 °C for every 1,000 m you climb, so a 2,000 m summit is often around 10 °C colder than the valley below.