How to read a weather forecast for a bike ride

Why doesn't a town forecast work for a bike ride?

A town forecast describes one place at one time, but a ride is a line through the landscape that lasts hours. A useful cycling weather forecast follows you, giving the weather for each part of the route at the time you'll be there.

Picture a 100 km (62 mile) loop that starts at 07:00 and finishes before midday. The forecast you check at breakfast is for your start town at that hour. By 11:00 you may be 80 km (50 miles) into the ride on a coast road, after the wind has swung round and strengthened.

Local winds show the problem worldwide. In Perth, Australia, the sea breeze known as the Fremantle Doctor almost always arrives from the south-west in the late afternoon, says the Bureau of Meteorology. On the New South Wales coast, the Bureau defines a southerly buster as an abrupt change to southerly winds above 54 km/h (34 mph). Sea breezes, fronts and afternoon showers reshape rides in Europe and North America too.

The answer is a route-timed forecast: split the route into short stretches, work out when you'll reach each one, and read the forecast for that place at that hour.

How do you read wind against your road?

Turn the forecast wind into a headwind, crosswind or tailwind for the direction each road runs. A wind is named for where it comes from, so a westerly blows into the face of a rider heading west.

That's the World Meteorological Organization (WMO) convention, measured clockwise from true north. The angle between the wind and your road decides how much of it you feel head-on.

Air resistance rises steeply with the speed of the air hitting you, so a headwind costs far more time than a tailwind gives back. See how much a headwind slows you down for the numbers, cycling in the wind for the full picture and wind direction explained for compass points and degrees.

Want this for your own route? Windline shows the wind for every stretch, timed to your pace. Free. Make a free ride page →

What's the difference between gusts and sustained wind?

The sustained wind is the average over 10 minutes; the gust is the strongest 3-second burst. The average sets how hard you'll work, and the gust decides whether you hold your line.

The Met Office measures both on a 10 m (33 ft) mast. In its app, the gust is the highest speed expected between one time slot and the next. A forecast of 20 km/h (12 mph) gusting 50 km/h (31 mph) can push you sideways on an exposed bridge in a way a steady 30 km/h (19 mph) won't. Read more on gusts versus sustained wind, and use both numbers in our table of how windy is too windy to cycle.

Why does the wind on the road feel different from the forecast?

Because the forecast is for 10 m (33 ft) above open, flat ground, the WMO standard height, and you ride much lower. Hedges, trees and buildings slow the wind near the road; bridges, ridges, causeways and coasts leave you exposed to all of it.

The same forecast can feel like a breeze in a wooded valley and a wall of air on an open dyke. Look at the map for exposed stretches, especially where the road turns side-on to the wind. Our guide to wind speed at ground level explains why.

What does "chance of rain" actually tell you?

It's the chance of at least a small, measurable amount of rain at a point during the period shown. It says nothing about how long or how hard it will rain.

The US National Weather Service counts 0.25 mm (0.01 in) as measurable. Its forecasters multiply their confidence that rain will arrive by the share of the area it should cover: 80% sure of rain over half the area gives a 40% chance at any point. The Met Office's hourly figure is the chance of at least 0.1 mm (0.004 in) in that hour.

On a bike, the amount matters more than the odds. Read the rain total in mm (inches) per hour beside the percentage: a high chance of a trace is a different day from a modest chance of a downpour. Our explainer on what chance of rain means adds a rider's rain-intensity table.

How should you read temperature and heat?

Read the temperature for the hours you'll be riding, not the day's maximum or the reading at your door. On a summer morning ride the hottest hours come near the end; in winter the coldest air often sits on early descents.

The Met Office's feels-like temperature takes wind speed and humidity into account. Your own speed matters too: moving air cools you on the flat, while a slow climb in the sun takes that breeze away. Our guide to cycling in the heat covers heat bands, hydration and warning signs, citing sports-medicine guidance.

How do weather models work, and why do they disagree?

A weather model is a computer program that starts from millions of observations, splits the atmosphere into a 3D grid and steps the physics forward in time. Centres use different grids, physics and starting data, so their answers drift apart, especially beyond a few days.

ECMWF receives 800 million observations a day, and about 60 million pass quality control for use in its model. Anything smaller than the grid, such as a single valley or headland, gets smoothed out. These three global models sit behind many weather apps:

NOAA has proposed taking GFS to about 9 km (6 miles) from October 2026. National models go finer: the Met Office's UK model uses 1.5 km (1 mile) squares. ECMWF also runs 51 slightly different forecasts, an ensemble, to show the range of outcomes. When models agree, plan with more confidence; when they don't, plan for both. Our comparison of ECMWF vs GFS explains how they differ.

How far ahead can you trust a forecast?

Trust it more as the ride gets closer. Small errors in the starting conditions grow as a forecast runs further ahead, as the Met Office puts it, so detail fades with every extra day.

Forecasts have improved steadily. The Met Office says its four-day forecast is now as accurate as its one-day forecast was 30 years ago. ECMWF reported in 2010 that its headline score for large-scale weather patterns had improved by about a day per decade, and it describes the medium range as up to about two weeks.

Our rule of thumb for riders:

• 1–3 days ahead: good enough to plan timing, route direction and kit around wind and rain.
• 4–7 days ahead: good for the pattern, such as which day of the weekend looks calmer.
• Beyond about 10 days: trends only.

The exact timing of a front or a shower is harder to pin down than the day's temperature. Our explainer on how accurate wind forecasts are covers lead time in detail.

How does a route-timed forecast work?

It splits your route into short stretches, works out when you'll reach each one from your pace, and reads the forecast for that place at that hour. It then compares the wind direction with the direction of each stretch of road.

Here's the timing for a 100 km (62 mile) route starting at 07:00, at 25 km/h (16 mph) on the flat and 12 km/h (7 mph) up a 6 km (4 mile) climb, with a 30-minute café stop:

The forecast for the last 40 km (25 miles) is the one for 10:00 to 12:00, not 07:00. If those kilometres follow a coast and an onshore breeze is due at 11:00, the breakfast forecast misses the hardest part of your day. Stretches of about 5 km (3 miles) are short enough to catch most changes of road direction.

You can also do it by hand with a weather map's time slider, as in our guide to [using Windy for cycling](/blog/windy-for-cycling/). If you plan in Strava, see [how to see the weather along a Strava route](/blog/strava-route-weather/).

What should you check in a cycling forecast?

Check eight things, roughly in order of importance for most rides. The table links each to the guide that covers it.

Which forecast terms do riders need to know?

These are the terms that come up most when you read a forecast for a ride.

• Mean (sustained) wind: wind speed averaged over 10 minutes at 10 m (33 ft) above open ground.
• Gust: the highest 3-second average wind speed within a period.
• Headwind component: the part of the wind blowing straight against your direction of travel.
• Crosswind: the part of the wind blowing across your direction of travel.
• Ensemble: a set of forecasts started from slightly different conditions, whose spread shows the uncertainty.
• Lead time: how far ahead of the event a forecast is made.
• Grid spacing: the distance between the points a model calculates.
• UTC: Coordinated Universal Time, the clock that names model runs.

How do you put it all together on a real ride?

Check broadly a week out, in detail the night before, and confirm that morning. Each check answers a different question.

1. A week out: look for the pattern only, such as a windy weekend, a hot spell or a wet front. Use it to pick a day, not your kit.
2. Two to three days out: compare models. If they agree on wind direction and strength, plan your start time and which way round to ride. See the best time to start a long ride.
3. The night before: run a route-timed forecast with your real start time and pace. Read every stretch for headwind, exposed gusts, rain amount and late-day heat, and check for official warnings. Then decide whether to go, start earlier, reverse the loop, shorten or postpone, and tell the group.
4. The morning of: check the latest model run, any warnings and the rain radar near the start. If the gusts have climbed into the risky rows of our too-windy table, make the call before you leave.

Official weather warnings always override any rule of thumb, including ours. To compare the tools that do the timing for you, see the best weather apps for cycling.