This weather map is published by the US Department of Agriculture. Observations were taken from 8am to 8pm where barometers reduced to Sea Level and 32degrees Fahrenheit. The heavy dotted lines inclose ares of marked changes in temperature during the past 24 hours. Shaded areas show regions of precipitation during the pat 12 hours. Arrows point in the direction the wind is blowing. The use of symbols is interesting here, as they indicate weather being clear, partly cloudy, cloudy, with rain, snow, etc. The amount of text that accompanies the map reflects the weather conditions and general forecast. It is interesting that these maps had to be published daily based on a network of national sites communicating climate data back and forth.