Preparedness - Wind Chill

nal The wind chill is based on the rate of heat loss from exposed skin caused by combined effects of wind and cold. As the wind increases, heat is carried away from the body at an accelerated rate, driving down the body temperature. Animals are also affected by wind chill.

Wind Chill Temperature Chart

Wind Chill Chart

Wind Chill (F) equals 35.74 plus 0.6215T minus 35.75(V0.16) plus 0.4275T(V0.16)

T - Air Temperature (F)

V - Wind Speed (Miles Per Hour)

New Wind Chill Index

This winter, the National Weather Service and Meteorological Services of Canada will use a new Wind Chill Temperature Index, designed to calculate a more accurate reading of how the cold air feels on the human skin.

How the New Index Works

Since 1945, the United States and Canada have used an index, which relied on observed winds 33 feet above the ground, and focused on how fast the cold temperatures-combined with winds-made water freeze. The new index accounts for the wind effects at face level, and a better calculation for body heat loss. For example, under the old index system, a temperature of 20 degrees, with 15 miles per hour wind, translated into a reading of five degrees below zero. The new index calculation would translate the same conditions to six degrees above zero. The new index is based on:

  • Wind speed calculated at the average height of the human face, about five feet (the human face is most often exposed to the cold).
  • Updated heat transfer theory, which factors heat loss from the body to its surroundings during cold, windy days.
  • A consistent standard for skin tissue resistance.
  • Clear night sky conditions.
  • A lowered calm wind threshold from four miles to three miles.

National Weather Service