Windchill 2nd Edition (UMAP)

This Module introduces a formula for heat loss in cold air and develops former and contemporary formulas for heat loss and windchill, in both metric and U.S. customary units.

This is the 2nd edition of a Module that was originally published in Vol. 5, No. 4 of this Journal in 1984 and reprinted in UMAP Modules (1985) 235–252 (Lexington, MA: COMAP). This revised edition has been updated to incorporate the change to the Wind Chill Equivalent Temperature index that was instituted in 2001; it compares that index with the earlier index examined in the first edition of the Module. Sections 6 and 7, on the post-2001 Wind Chill Equivalent Temperature—and accompanying exercises, answers, and references—have been added, dated references removed, and editing done by Paul J. Campbell (Beloit College).

Table of Contents 

1. Introduction

2. The Heat Loss Formula

2.1 Origins
2.2 Discussion

3. The Limiting Effect of Wind Speed

4. Converting to U.S. Customary Units

5. Old Windchill Equivalent Temperature (Pre-November 2021)

5.1 WCT in US Customary Units 
5.2 WCT in Metric Units

6. The Post-2001 Windchill Equivalent

7. Postscript

8. Model Exam

9. Answers to the Exercises

10. Answers to the Model Exam

References 
About the Authors

Air motion, or wind, has a significant impact on the temperature that a person feels, often making it seem colder than it actually is. Under certain circumstances, what is “felt” can be a more important indicator of the effects of temperature than temperature itself. Thus, attempts have been made to quantify the effect that wind has on the temperature that one feels.

Research into the problem of how much heat a body will lose under given conditions of temperature and wind has resulted in various windchill indexes that represent the equivalent temperature that exposed skin would feel with little or no wind. Exposure to cold temperatures associated with windy conditions can be dangerous if proper precautions are not taken. Explorers of polar regions and seamen were some of the first people who needed to assess such risks. Farmers, firefighters, and others involved in outdoor activity need to be concerned about the chilling effect of the wind. So weather reports on radio and television commonly include information about “windchill” if it is a cold, windy day.

How “chilly” one feels depends upon a number of things besides wind and temperature, such as state of nourishment, individual body metabolism, and the moisture content of the air. However, a windchill index is a good guide to the type and amount of clothing that will be needed for given conditions of wind and temperature and is used widely for such purposes.