Every bike commuter has a rain threshold. The problem is that most of us apply it inconsistently — riding into a soaking because the sky "looked fine," or bailing to a crowded train on a morning that turned out dry. The fix isn't toughness; it's a faster, better decision.
Not all rain is equal
The forecast word "rain" covers a 100x range of actual experience. What matters on a bike:
Intensity (mm/h), not probability. A 90% chance of 0.3 mm/h is mist — you'll barely notice it at 20 km/h. A 40% chance of 6 mm/h is a possible soaking. When your app shows a rain icon, tap into the hour and read the millimetres.
- Under 0.5 mm/h — rideable in normal clothes; glasses help.
- 0.5–2 mm/h — rain jacket territory; you'll arrive damp but fine.
- 2–5 mm/h — full kit (jacket, overtrousers, shoe covers) or reschedule.
- Over 5 mm/h — visibility and braking degrade for you and for drivers. Delay or bail.
Temperature multiplies everything. 15°C rain is an inconvenience; 4°C rain is a safety issue — wet plus wind chill drains core temperature fast, and your hands stop working before you notice. Below ~7°C, treat rain one category worse than the intensity suggests.
Wind is the hidden variable. A 30 km/h crosswind with rain is harder riding than heavier rain in still air. Gusts above 45 km/h with wet roads is bail weather regardless of rain intensity.
The 60-minute trick
Rain is bursty. Radar loops show it moving in bands with gaps, and commutes are short — 20 to 45 minutes for most riders. That means timing beats gear: shifting your departure 15–20 minutes routinely turns a wet ride into a dry one.
Before a marginal ride, look at the radar's motion, not just the current frame. If a band is about to pass, leaving after it beats leaving before it — even if the "before" frame looks dry.
Decide the night before (mostly)
The best rain decisions are two-stage:
- Evening: check tomorrow's commute window. If it's clearly dry or clearly awful, decide now (kit laid out, or train ticket sorted).
- Morning, 30 minutes out: confirm with fresh data. Overnight forecast drift is real — the evening's "dry by 8" regularly becomes "rain until 9."
The failure mode is doing only stage 1 and riding on stale data.
Automating the check
The two-stage check is exactly what Waycast does for you. Save your commute once — home to work, by bike, weekdays at 8:10 — and it samples the forecast along your route at the times you'll be at each point, not just at your front door. Before departure you get a short briefing written for a rider: rain intensity, wind, and whether delaying helps ("Band clearing by 8:25 — push departure 15 min and you're dry").
If the forecast changes materially between your evening glance and the morning, Waycast notices and sends one heads-up. And if you're running late, you can push the departure back and it re-checks the new window — no GPS, no tracking, just the plan you gave it.
Three trips are free, no card required. Save your commute and make the ride/bail call in five seconds instead of five minutes.