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About

Weather for the track, in racing language

Raceway Weather is an independent fan site: hour-by-hour forecasts for 242 American race tracks, read the way a crew chief reads them.

What this is

Pick a track and you get the weather right now, the next 24 hours by the hour, the week ahead, and the numbers racers set up by. The home page puts every track on one map so you can see where it is raining, blowing or baking at a glance. The 242 tracks start with a hundred headline venues: the major NASCAR and IndyCar ovals, the road and street courses, the historic short tracks, the big dirt ovals and the NHRA drag strips. The rest are the regional tracks the touring series visit: World of Outlaws, High Limit, Lucas Oil, CARS Tour and ARCA. Headline tracks refresh every 45 minutes; regional tracks every three hours, or every 45 minutes in the days before a big event there.

Tap the star on any track to keep it at the top of the home page, with your recent visits under it. The list is kept on your device; Raceway Weather Pro members keep it on their account, on every device.

We do not carry results; the series and the tracks do that well. We carry the weather, for racers, crews and fans deciding whether to load the trailer, buy the ticket or bring the rain suit. Missing your track? Submit your raceway and we will add it.

How the flags work

Every day at every track gets one flag, judged over the racing hours (9 am to 10 pm in the track's time zone). The worst hour sets the flag.

The map's "roughness" list ranks tracks 0 to 100 by how much the forecast should bother a race day: rain chance and amount, gusts over 18 mph, lightning potential, heat past 95 °F, cold under 32 °F and snow, again over the racing hours. It is a ranking aid, not a prediction of a postponement.

The racer numbers

These come from the same forecast (air temperature, dew point, station pressure, sun, wind) through the standard formulas. They are estimates from a weather model, not sensor readings at the track.

Density altitude
The altitude in the standard atmosphere that has the same air density as the air at the track right now. Hot, humid and low-pressure air "feels" higher to an engine and makes less power; drag racers and tuners watch it hour by hour. We use the National Weather Service formula from air temperature, dew point and station pressure.
Air density and RAD
Kilograms of air per cubic metre, and the same thing as a percentage of the sea-level standard (1.225 kg/m³), which some tuners call relative air density.
Water grains
Grains of water vapour per pound of dry air (7,000 grains to the pound). The humidity number on drag-strip weather stations.
Track temperature
An estimate of the surface temperature from the air temperature, the solar radiation, the wind and the surface (asphalt heats most, concrete least, dirt in between). In full midday sun asphalt runs 20 to 30 °C above the air; at night it sits at or just under it. Real surfaces vary with colour, age, moisture and shade, so treat it as a guide.
Dew point
The temperature the air would have to cool to for dew to form. A tight gap between air and dew point at night means fog and a damp surface in the morning.
Barometer
Sea-level pressure and whether it rose or fell over the last three hours. Falling fast usually means weather is coming.
Dirt surface
On dirt tracks only: dry, tacky or wet, from the rain of the last 48 hours and the moisture in the top centimetre of soil in the model. Track prep decides the real surface; this says what the sky gave the crew to work with.

Where the data comes from

The family

Raceway Weather is the fourth site from the team behind GPWeather.com (Formula 1), CupWeather.com (NASCAR race weekends) and CFBWeather.com (college football). It is paid for by advertising and is not affiliated with NASCAR, IndyCar, IMSA, the NHRA, any sanctioning body or any track.

Contact

Use Feedback in the footer for corrections, bugs and tracks you want added, or write to [email protected].