How It Works

The RunFeel number

The single number driving every recommendation is RunFeel, an adjusted temperature that reflects how your body will actually experience the conditions, not just what the thermometer says.

It starts with the feels-like temperature from the weather API. Feels-like already folds in wind chill and humidity, so it is closer to lived experience than the raw air temperature.

From there, RunFeel applies a series of warming shifts based on how you run. The harder and longer you go, the more heat your body generates:

These shifts reflect the real heat your body generates while running. A fast runner logging 10 miles in cold weather will warm up significantly more than someone jogging two miles. The kit they need is different, and RunFeel captures that. The shifts stack, but the combined total is capped at +20°F so extreme combinations never run away.

This is not guesswork. Sports-medicine and coaching guidance has long advised runners to dress for roughly 10–20°F warmer than the air temperature, because exercise turns your body into a heat engine. RunFeel does that math for you (tuned to your profile, pace, and distance) and the +20°F cap mirrors the top of that established range. The research behind it is listed below.

Temperature bands

Once RunFeel is calculated, it falls into one of six bands. Each band maps to a base layer stack: the core garments we recommend regardless of wind or rain.

Wind and rain modifiers

Wind and precipitation are checked on top of the temperature band and can add specific items to the recommendation:

• Wind above 15 mph: Wind shell recommended. If it is also below 45°F, ear coverage is added, since exposed ears lose heat quickly in wind.
• Rain above 0.5 mm/hr: Water-resistant outer layer recommended, plus a brimmed hat or cap to keep rain out of your eyes.

Cold and heat safety

In the most extreme bands, RunFeel adds safety reminders on top of the gear. The strongest warnings are tied to the actual wind chill or heat index, not the run-adjusted number, so they only appear when conditions genuinely warrant it:

• Extreme cold: Always a reminder to cover ears, hands, and face, the spots that lose heat fastest. If the true wind chill is near 0°F or below with wind present, a frostbite warning is added, since exposed skin can freeze.
• Extreme heat: Always a prompt to hydrate and ease your pace, because your body has to work harder to cool itself. Once the heat index reaches 90°F, a heat-illness warning is added: run early or late, and stop if you feel dizzy.

The research behind it

RunFeel and the gear logic are grounded in published sports-medicine guidance, national weather-service data, and exercise-physiology research, not personal opinion. The sources we leaned on:

• The "dress 10–20°F warmer" rule: ACSM expert guidance on cold-weather exercise: runners dressed for standing around are overdressed once moving, so plan for the heat you will generate.
• Why pace and distance add heat: American Physiological Society review of exercise thermoregulation: steady-state core temperature rises with metabolic rate, which is exactly what the pace and distance shifts model.
• Wind chill and the cold-weather modifiers: NOAA / National Weather Service wind chill chart: the basis for treating "feels like" as wind-adjusted and for covering exposed skin once the wind picks up.
• Layering and the "slightly cold at the start" cue: REI Expert Advice on cold-weather running: the base / insulating / shell system, and starting a touch chilly so you are comfortable once warmed up.
• Running in the rain: Runners Need gear guide: water-resistant shell plus a brimmed cap, and not overdressing when it is mild.
• UV and sun protection: US EPA UV Index scale (aligned with the World Health Organization): the 3 / 6 / 8 / 11 thresholds behind our sun-protection tips.

These are general guidance for healthy adults, not medical advice. Conditions and bodies vary, so trust how you feel over any chart.

Where weather data comes from

Weather is fetched from a few trusted public sources:

• National Weather Service (NOAA): Primary source for U.S. locations. Detailed local forecasts plus official weather alerts.
• OpenWeatherMap: Covers international locations, and a backup for the U.S. Current conditions and short-range forecast from multiple meteorological sources.
• Open-Meteo: Final fallback, and the source of our hourly air quality (US AQI) and UV index. Open-source weather data from national meteorological services.

Weather data by Open-Meteo.com, licensed under CC BY 4.0.

Weather conditions can change rapidly. RunnersKit shows you a snapshot at the moment you ask, not a guarantee of what you will encounter on the road. Always check conditions before heading out, especially in severe weather.

Affiliate links

Some gear recommendations include affiliate links. If you purchase through one of these links, RunnersKit may earn a small commission at no additional cost to you. Affiliate relationships do not influence which gear is recommended. Every selection is driven entirely by RunFeel and current conditions, not by commission rates.

What we do not collect

No account is required to get a recommendation. When you use RunnersKit as a guest, we do not store your location, your outfit, or anything that identifies you. Affiliate link clicks are counted in aggregate. No personal data is attached to a click event.