Heavy to excessive rainfall may lead to flooding today over southwest Pennsylvania into northern West Virginia, and western Maryland. Severe thunderstorms are possible this afternoon and evening in the Mid-South and across Eastern North Carolina. An extended period of hot weather is forecast for parts of coastal southern California including Los Angeles from today through Thursday. Read More >
Density Altitude: The altitude in the standard atmosphere at which the air has the same density as the air at the point in question. An aircraft will have the same performance characteristics as it would have in standard atmosphere at this altitude.
High Density Altitude: A condition of the atmosphere that reduces an aircraft’s performance capability to below a level of standard performance at a specified altitude.
Cold, Dry Day![]() Low Density Altitude |
Hot, Humid Day![]() High Density Altitude |
Air density is determined by Pressure, Temperature, and Humidity.
On a hot, muggy day, the air becomes "thinner" or less dense, and its density at a pilot's location is equivalent to a higher altitude in the standard atmosphere. Thus the term "high density altitude."
Pilots must determine if high density altitude will impact their flight by calculating density altitude and checking their aircraft performance charts.