Rain on Route Plan a trip

How the verdict is made

A normal weather app tells you about one place. A road trip passes through many places over several hours, so Rain on Route checks each stretch of road at the hour you will actually be on it.

  1. Find the road

    Your start, any stops and your destination are turned into map points, and the road route between them is fetched from OSRM, an open routing service built on OpenStreetMap.

  2. Plant a milestone every 25 km

    Points are placed along the road roughly every 25 km, up to 25 points for long trips, so no stretch is skipped.

    Chennai → Madurai, 456 km → 20 milestones

  3. Work out when you reach each one

    Arrival time at each milestone comes from your departure time and the slower of your vehicle's speed and the route's average speed.

    Two-wheeler 45 km/h · Car 70 km/h · Bus 50 km/h

  4. Ask the forecast for that exact hour

    One request asks Open-Meteo for the hourly forecast at every milestone. Only the hour you arrive is used. Three independent weather models (ECMWF, GFS and ICON) are compared to see if they agree. Milestones you reach in the next 90 minutes use a 15-minute forecast instead.

  5. Grade each stretch and give one verdict

    Each milestone gets a rain level from the millimetres expected in that hour. The share of wet milestones gives the verdict, and the worst stretch is named with its place and time.

    "Rain on parts of the route. Heavy rain near Villupuram around 3:10 pm."

Rain levels

LevelRain in that hour
Dry< 0.2 mm, rain chance under 50%
Showers likely< 0.2 mm, rain chance 50% or more
Rain chance: the share of runs with 0.2 mm or more in the ECMWF (51 runs), GFS (31) and ICON (40) ensembles, averaged so each system counts equally.
Light0.2 – 2.5 mm
Moderate2.5 – 7.5 mm
Heavy> 7.5 mm

Rain is rain: any level from Showers likely up counts as wet, the same for a bike, car or bus. Dry = no rain at any milestone. Mostly dry = under 25% wet. Rain on parts = 25–60%. Rainy trip = over 60% with Light rain or more, or more than 50 km of heavy rain in a row.

Confidence

High
Trip within 3 days, the weather models agree at most milestones, and under a quarter of them are a coin flip (rain chance 30–69%, or Showers likely).
Medium
4–7 days ahead, or the models disagree.
Low
8–15 days ahead. Check again closer to the trip.
Typical
Beyond 15 days there is no forecast. You see how often it rained in the same week over the last 5 years.

Also on the road

Fog
Visibility under 1 km at any milestone.
Gusts
Wind gusts of 40 km/h or more.
Heat
Feels like 38 °C or more.
Thunder
A thunderstorm forecast at any milestone. The first one is shown.
Dark
The first milestone you reach after sunset.
Wet roads
5 mm or more of rain in the last 24 hours at a milestone, for trips leaving within 12 hours. Estimated from weather models, not rain gauges.
Pack
A short list from the verdict and warnings: raincoat, rain covers, water, headlights, a warm layer.

Extras

Break
Before the first moderate or heavy stretch, named fuel, food and toll stops within 2 km of the road, from OpenStreetMap.
Other road
Trips without stops are also checked on up to two alternative roads. Tap a road to see its forecast.
Find on the road
Premium: CNG, EV charging, LPG autogas, puncture shops, hospitals, toilets and lodges within 2 km of the whole road, from Ola Maps, searched town by town along the route (town names from GeoNames, CC BY 4.0). Some places may be missing, so call ahead. The free version allows 5 searches every 3 hours.
Radar
Rain actually falling now and over the last 2 hours, from RainViewer. It shows what is happening, not a forecast.
Did it rain?
After your trip, one tap tells us if the verdict was right. That is how we track accuracy.