What is historic weather, and when is my route best?

What it is

A forecast only reaches about 10 days ahead. Historic weather covers the rest of the year: what your route has actually had, on these dates and at the hours you’d ride, over the last ten years.

It comes from Copernicus ERA5, the European record of the world’s weather, hour by hour, for every 25 km square of the planet. Windline reads 2015 to 2024 along your route and runs it through the same maths as the forecast: the same headwind and tailwind, the same Good, Fair and Tough.

It’s free, for every event.

When is this route best?

On your event in the dashboard, tap Plan with historic weather. It opens a card with:

• A plain answer: for example “May to September is this route’s best time. Good on about 9 days in 10, the wind’s usually behind you (about 11% less effort), hardly any rain and 14–20°.”
• The twelve months, with your own dates marked Your dates. Switch between:
  • Wind: how many days in 10 were Good, Fair or Tough, as ten squares a month;
  • Rain: how many days in 10 had at least 1 mm;
  • Temperature: the usual high and low.
• Tap a month for its detail: the mix of Good, Fair and Tough days, the usual wind and what it does at your pace, the rain, and how often it’s hot or cold in the morning.

It works out every day of your event, at your own start times, pace and stops, so a 12-day tour is judged as the whole tour.

Tap the arrow to fold it away. It stays on your event even inside the last 10 days and after the event, for planning the next one.

Worldwide figures first, then your route’s own records

When you first open it, you see the worldwide figures straight away: the averages for your route’s part of the world. Meanwhile Windline fetches your route’s own records: every real day of the last ten years, hour by hour, ridden at your times. You’ll see “Checking this route’s own records” while that happens, usually 10 to 15 minutes for a long tour.

Then the card switches by itself, and says “From this route’s own records”. The Good, Fair and Tough days are now real days: every date of every year, rated one by one.

Days more than 10 days out

Each day that’s too far ahead for a forecast shows its historic weather instead, with an outlined rating, for example “Tailwind, 12% less effort · rain 2 days in 10 · 11–16°”, and when its forecast opens. From 10 days out, the live forecast takes over by itself. See when the forecast opens.

What it can’t tell you

• It’s not a forecast. It’s what usually happens, not what will happen this year.
• It sees the weather in 25 km squares. A valley wind, a sea breeze in a bay or the shelter of a city street can differ.
• The ratings come from the wind, gusts, heat and cold at your hours, and the rain on the day.

Weather records: Copernicus Climate Change Service, ERA5 (2015–2024). Contains modified Copernicus Climate Change Service information.

Historic weather is on the website now, and comes to the iPhone app in its next update.