Your window
Your run + 15 min buffer, checked hour by hour.
Your milesWhere will you run?
Enter a location above to compare the weather.
What to expect
Ratings follow published running and weather-safety research. Forecasts can be wrong, so check the sky and any alerts before you head out.
Every start time
Your start times
Each cell is a 30-minute start that covers your full run and a 15-minute buffer. Night sits on the darker ground, with the half-light of dawn and dusk between; the bar under the strip is how long you will be out. Select a cell for the full assessment.
Your start times will appear here.
The hours ahead
Wind, temperature, dew point and rain chance for the forecast point.
Find your window to load the forecast.
| Local time | Conditions | Temperature | Dew point | Humidity | Wind | Gusts | Rain chance |
|---|---|---|---|---|---|---|---|
| Enter your run details above. | |||||||
Before you lace up
Waterfront wind can be stronger than the forecast point. Flooding, fallen branches and closed paths can persist after a storm. Forecasts describe one point; conditions vary along a route.
How the running windows are assessed
- A planning guide built from published sports-science and weather-safety research, not a guarantee. Forecasts can be wrong.
- All times use the selected location's time zone. Your time range controls when you start; the run may finish after the latest start.
- Every overlapping forecast hour is checked through your full distance and a 15-minute buffer, including a partial final hour. Start times are compared every 30 minutes.
- Good conditions: none of the checks below were triggered. Fair conditions: something will make the run harder or less comfortable; the reasons say what. Poor conditions: a limit we do not recommend running past. Forecast incomplete: we could not check everything.
- Poor at air temperature ≥95°F, feels-like ≥100°F, air temperature ≤10°F or feels-like ≤-18°F (frostbite risk in about 30 minutes).
- Poor at sustained wind ≥25 mph or gusts ≥30 mph (≥25 on waterfront routes). Missing gust forecasts are estimated at 1.5× the wind speed, never treated as calm.
- Poor when thunderstorms are forecast with “Chance” wording or stronger, or with a rain chance ≥40%; “Slight Chance” or “Isolated” thunder is fair on park routes and poor on waterfront routes.
- Poor for freezing rain, sleet, ice pellets, heavy snow or blizzard; for 40°F or colder with rain likely and wind ≥15 mph on runs over 60 minutes; and for dense fog with 10+ minutes of darkness.
- Official NWS alerts are matched by name: warnings for tornadoes, severe storms, flash floods, extreme heat or cold, winter storms and high wind are poor; advisories and watches are fair; coastal flood, surf and rip current alerts are poor on waterfront routes only.
- Fair at air or feels-like ≥80°F, or dew point ≥65°F (sticky; ≥70°F very muggy). Runs over 90 minutes use lines 5°F lower. Dew point, not relative humidity, is the moisture signal.
- Fair at sustained wind ≥15 mph (≥13 waterfront) or gusts ≥20 mph (≥18 waterfront).
- Fair at rain chance ≥70%, or ≥60% with ≥0.10 inch expected during the run, or ≥0.25 inch in an hour. Lower chances are shown as a note.
- Fair for cold rain (≤50°F with rain likely; 5°F warmer for runs over 90 minutes or slower than 12 min/mile), feels-like ≤14°F, or ≤32°F with precipitation possible. Dry cold above that gets a dress-warmly note.
- Fair for snow, fog or heavy rain in the forecast, patchy fog in the dark, or 10+ minutes of the run in the dark: before dawn or after dusk, the ends of civil twilight. The half-light between dawn and sunrise, or sunset and dusk, is noted but does not change the rating.
- Ranking among windows with the same rating: distance from a 45–55°F sweet spot, dew point above 55°F, wind (weighted by its square, as headwind cost grows), gusts above the sustained wind, rain chance and minutes of darkness, averaged over the time you are out.
- UV index comes from Open-Meteo for every location (NWS hourly forecasts do not include it) and is shown with sun-protection advice from 6 (high). It never changes a rating.
- Missing temperature, humidity, wind, rain chance or descriptions, or incomplete or stale forecasts, give "Forecast incomplete" instead of a rating.
- If US alerts cannot be verified during a routine outage, the window is rated fair with that reason. Outside the US, official alerts are not supplied; check your local weather service.
Forecast sources & freshness
US weather from NWS. International forecasts and the UV index from Open-Meteo. Location data from GeoNames. Forecasts refresh while you use the app.
Read the official alerts —
Alerts appear after you find your window.
How PuddleRunner works
Type a town or postal code, or use your location, and PuddleRunner checks every 30-minute start across today and tomorrow, a date you pick, or the whole week. Each start is rated for the full length of your run plus a 15-minute buffer, so a dry 6 AM start that runs into a 7 AM downpour is rated for the downpour.
Forecasts come from the National Weather Service in the United States and from Open-Meteo everywhere else. Sunrise, sunset and twilight are computed for your forecast point. Nothing is guessed: when part of the forecast is missing or stale, the start says Forecast incomplete instead of inventing a number.
There is no account and nothing personal is stored on our servers. Your settings stay in your browser, and a plan link carries them so a running partner sees the same comparison.
What the ratings mean
Among starts with the same rating, the best one is the coolest, calmest and brightest, averaged over the time you are out. Every limit and the research behind it is on the running weather science page; who makes this and why is on the about page.