The importance of definitions: chance of rain

Tomorrow’s weather forecast for Carlisle, PA, is: Windy with showers. High 58F. Winds SW at 20 to 30 mph. Chance of rain 40%. First of all, 58 degrees on December 28? Sweet! But what does “chance of rain 40%” mean? Does it mean that there is a 40% chance that it will rain at my…