Erica's Answer:
Officially, wind chill values are only calculated when the temperature is below 40 degrees and the wind speed is greater than or equal to 3 mph. In recorded history we've never had temperatures below 40 degrees in Philadelphia during the summer, but if it happened, and there was a breeze blowing, then we would definitely have a wind chill! The same is true for a heat index in the winter. Again, officially, heat index values are only calculated when the computed value is greater than or equal to 80 degrees. An example of heat index conditions of 80 degrees would be if the air temperature is 78 degrees and the dewpoint is 70. A time when the heat index became a factor in the winter would be in March 1990, when we hit incredible record highs of 83, 84, 85 and 81 degrees on March 12, 13th, 14th, and 15th, respectively. Though it was technically still winter, the heatwave of March 1990 had a lot of people thinking about spring- myself included!- Erica
