There is ample evidence that climatic conditions affect the productivity of construction laborers. The productivity loss is related to the specific skill being performed and the interaction of temperature, humidity and wind. Depending upon these factors the loss in production, as measured against production at 70 degrees F and 50 percent relative humidity with wind of tow miles per hour, can be as great as 75 percent or as small as 12 percent. The data compiled in Table 1 found in the article given for low temperatures with still air and a relative humidity of 40 to 60 percent. When a wind is blowing. The "Effective Temperature" is obtained by lowering the measured temperature one degree for each one mile per hour of wind, using a practice adopted by environmental engineers. On a 40 degree F day with a wind that averages 10 miles per hour one could say the effective temperature is 30 degrees F. Should the humidity raise to 80 percent the effective temperature is even colder, although the exact adjustment to be made is not given. Certainly the phrase "bone chilling" is associated with damp cold. Using the same rationale a table for high temperatures can be constructed. Although the percentage s shown in the article are estimates, they should provide working figures for job time planning. It is apparent that individual job factors and the specific workers involved will necessitate adjusting these estimates upward or downward. Such factors as the worker's adaptation to climate and his individual temperature sensitivity will account for variations.