Run & Ride: when to run and what to wear

One score for every hour, the best hour named, and the arithmetic shown.

On this page: the best time to run, the score, heat, what to wear, by temperature, and official warnings.

What this lens tells you

Switch the forecast to Run & Ride and the headline stops talking about jackets. It names one hour: the best one for a run in the next 30 hours. If that hour is close, it says "Go now". If no hour is good enough, it says "Treadmill day" and gives a reason.

Use it when you get to choose when you go. The "What to wear" card is dressed for the hour the page picked, which is not always the hour you are in.

Open the forecast with Run & Ride switched on.

What is the best time to run today?

The page scores every hour from now to 30 hours out and names the one with the highest score. The hour you are in counts, unless it has less than 10 minutes left. A later hour has to beat an earlier one by more than 0.05 of a point, so a tie goes to the sooner hour.

The best hour has to score at least 3. What the headline says next depends on how far off it is.

• If that hour is today, and it has started or starts within 90 minutes, the headline is "Go now".
• Otherwise the headline names the day and the hour and calls it your run. The search runs 30 hours, so the best time to run today is sometimes tomorrow. The page says so.
• If the best hour scores under 3, it is a treadmill day. That has a section of its own below.

When the page names an hour, the headline goes on to give that hour's air temperature, a word for the wind, and "dry". A wet hour can still win when every other hour is worse. Then the headline says "light rain" where it would have said "dry". Those words are fixed. The page uses them for any wet hour it names, whatever is falling and however much.

The "Why we say that" box gives that hour's numbers: feels like, the steady wind, dew point when the forecast has one, and air quality when we have a reading. If a wet stretch is under way or starts later today, the box names the first one as hours to skip.

The score, line by line

Every hour starts with 10 points. Nothing adds points. Each line below can only take them away.

So the hour we like best feels like 45 to 58°F, in daylight, dry, with wind at 12 mph or less and a dew point at 60°F or less. That is our taste in running weather. It is not physiology, and you may run warmer or colder than we do.

The scale is ours too. A score has no unit. Its job is to put the hours in order.

What counts as a wet hour

An hour is wet when the forecast calls it rain, drizzle, snow, a wintry mix or thunderstorms, and either the chance is at least 40 percent or the amount is at least 0.5 millimetre (about 0.02 inch). If the forecast uses one of those words and gives no chance, the hour counts as wet. When the forecast's word for the sky is anything else, it takes a chance of at least 60 percent and at least 0.3 millimetre (about 0.01 inch). In the United States there is one step before this test: an hour the Weather Service gives a chance under 25 percent is read as cloud whatever word it uses, so it falls under the second rule. It is the one test the forecast page has for a wet hour.

Is it too hot to run right now?

The page does not answer that with a yes or a no. It has no line where a run becomes unsafe, and it does not know you. What it has is the score, and heat costs points.

• Above a feels-like of 58°F, an hour loses 1 point for every 4.5 degrees.
• Above a dew point of 60°F, it loses 1 point for every 4 degrees.
• If the hour the page picks feels like 78°F or more, the "Why we say that" box adds: "It is a warm one: start early and carry water."
• On a treadmill day with no rain on the way, if the feels-like goes above 88°F in the next 12 hours, the reason given is "It is too hot to enjoy."

So the page answers a nearby question: which hour is the least bad. All else equal, a cooler hour beats a hotter one until the feels-like is down to 58°F. If the page says "Go now" on a hot day, it means now is the best hour on offer. It does not mean now is safe.

"Too hot to enjoy" is our opinion about comfort. Heat advisories and warnings come from the National Weather Service. In the United States the page shows them as written, above the headline. The score does not read them, so the page can name an hour while one is in force. Read the alert first. Whether the heat is safe for you is a question for you and your doctor, not for a forecast.

For the hour the page picks for your place, open the forecast with Run & Ride switched on and search for your town.

When the page says treadmill day

If no hour in the next 30 scores 3 or more, the headline is "Treadmill day" and one reason. The page checks these in order and gives the first that is true.

1. A wet stretch is under way, or one starts within 18 hours: "It rains most of the time that matters." The verb follows the forecast, so it can also be drizzles, snows, storms or "is wintry".
2. The feels-like stays below 20°F for the next 12 hours: "It stays brutally cold."
3. The feels-like goes above 88°F in the next 12 hours: "It is too hot to enjoy."
4. Wind goes above about 25 mph (40 km/h) in the next 12 hours, counting a gust at 75 percent of its speed: "Wind is the problem."
5. The air quality index is above 100: "The air is rough."
6. None of those: "Nothing lines up well."

The reason is a short answer, not the whole score. A day can fail on several counts at once. The page names the first on this list. The first check asks only whether a wet stretch is close. It does not measure how long the stretch lasts.

On a treadmill day there is no hour to dress for. The kit falls back to the average feels-like over the next six hours and says so: "No good hour for a run in the next day, so this is the plain kit." With no picked hour, the kit is dark if it is dark now, and wet if the forecast has precipitation now or starting within 8 hours. Ice is called possible when the average feels-like is 34°F or colder and that precipitation is anything but snow.

What to wear running, by temperature

The run kit goes by the feels-like temperature at the hour the page picked. That is not the thermometer, and it is not always now. Each row starts at its lower number and stops just short of the higher one.

The rest is added when the hour calls for it.

• Hands. Light gloves at 45°F or colder.
• Head. A beanie or ear band at 38°F or colder. Above that, a visor or cap if the hour is wet, or if it is dry daylight with a UV index of 3 or more.
• Shoes. Road shoes when the hour is dry. Shoes with grip when it is wet. Traction for your shoes when ice is possible, which for the picked hour means air at or below about 34°F (1°C) with a chance of precipitation of 30 percent or more.
• In the pack. A headlamp and a reflective band when the hour is dark. Water and a gel at 72°F or warmer. A dry shirt for after when the hour is wet, or at 36°F or colder. If none of those apply, a phone and a key. The pack line shows three things at most.

These are our picks, written down so you can argue with them. You know whether you run hot.

What to wear running at 50 degrees

At a feels-like of 50°F on a dry hour, the kit is a long-sleeve tech tee, running tights and road shoes. No gloves, and no hat unless it is daylight with a UV index of 3 or more.

That number sits on an edge in our rules, and near another. Just under 50°F the kit adds a light shell. At 52°F the tights become shorts. Gloves wait for 45°F.

All of that is feels-like. Wind chill is part of that number, so a windy 50 on the thermometer is dressed colder than a calm one. The methodology page says how we work out feels like.

If you ride

The lens is called Run & Ride. The page has one score, the one above, and it is tuned for running. There is no separate cycling score on the forecast page, and the kit is a running kit.

A rider can still use the hour it names. We think wind and a wet road matter more on a bike than this score allows. The service we built for assistants keeps a separate cycling score. It starts counting wind at 10 mph where the running score waits for 12, and it does not count warmth against an hour until the feels-like passes 82°F. The forecast page does not show it.

Official warnings come first

When the National Weather Service marks a warning as immediate, like a tornado warning, this lens stands down. The headline becomes the warning and what to do. There is no best hour and the kit is hidden. Follow the warning and your local officials before anything on this page.

Any other official alert is shown above the headline, and the score does not read it. The lens still names its hour, so read the alert first.

The alerts are the National Weather Service's, so the page has them for the United States only. Elsewhere it says so, and this lens never stands down. For warnings there, check your own country's weather service. If the page could not check for alerts, it says that too, and points to weather.gov.

What the page does not know

• The ground. A forecast cannot see the trail, the puddle at the bottom of the hill or the ice on a shaded corner. When the kit says "Pavement is dry", it means the forecast for that hour is dry. "Ice is possible" is worked out from the temperature and the chance of precipitation. It is a guess from the forecast, not a report from the road.
• You. Your pace, your health, and how you take heat and cold. The score is one opinion about comfort, applied to everyone.
• Lightning. The page reads the forecast's word for the hour. It does not detect strikes. An hour the forecast calls thunderstorms loses 8 points, which leaves it under the 3 it needs, so the page will not name it, with one exception. In the United States, when the Weather Service gives an hour a chance of precipitation under 25 percent, the page reads that hour as cloud, whatever the Weather Service calls it, thunderstorms included. That hour loses nothing, so the page can name it and call it dry. A slight chance of thunderstorms is still a chance, so read the forecast for the hour yourself. Each hour is scored by itself, so the page can still name the hour before one. A storm the forecast did not see is not in the score.
• Tomorrow's air. Air quality is the current reading from AirNow, United States only. The same number is applied to every hour we score. It is not an air quality forecast. Where there is no reading, the score leaves air out.
• The route. Traffic, street lights, shade, hills, and whether a path is open.
• The future. A forecast is a forecast. The hour we name is the best hour in the forecast, and the forecast can be wrong.

Who does know: the National Weather Service for warnings, AirNow for the air, whoever looks after the trail, and you.

For assistants

An assistant can ask our weather service directly. For a road run it uses the same score as this lens. For a ride it uses the separate cycling score. The page for agents says how to connect.

The other lenses

• Commute: rain and ice at the two ends of the working day.
• Hunt and fish: pressure, last light and thunder in the forecast.
• Home and yard: freezes, mowing windows and the sprinklers.
• Build and finish: dry stretches for stain and finish.
• Methodology: where the data comes from and how the sentence gets made.