National Weather Service United States Department of Commerce

Strong to Severe Storms in the Northern and Central High Plains; Very Hot Temperatures in South Texas and Florida

Scattered strong to severe thunderstorms capable of producing severe winds and hail are likely to develop this afternoon in the northern and central High Plains. Isolated large hail and heavy rainfall will also be possible in southwest Texas. The combination of high surface temperatures and high humidity will lead to heat index values up to 110 degrees in portions of south Texas and Florida. Read More >

High density altitude accounts for 7.3% of all U.S. aviation weather-related accidents.

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
Low Density Altitude
Hot, Humid Day
High Density Altitude
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.

High Density Altitude Hazards

  • Reduced Power (engine ingests less air to support combustion)
  • Reduced Thrust (propeller has less “grip” and jet exhausts less mass)
  • Reduced Lift (air exerts less upward force on the airfoils)
  • Longer takeoff roll is required
  • Smaller rate of climb
  • Lowers aircraft’s service ceiling
  • Longer landing roll required

High Density Altitude and Heat

  • The higher the altitude, the thinner the air.
  • Mitigation: reduce aircraft gross weight for safer operations
  • Hot
  • The warmer the air, the less dense it is.
  • Mitigation: flight operations early morning or late afternoon are safer
  • Humid
  • Not considered a major factor because the effect of humidity is related to engine power rather than aerodynamic efficiency
  • Mitigation: add 10% to computer takeoff distance and anticipate reduced climb rate
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    Day 3 Max Temp Day 4 Max Temp