Once you know what these mean, reading weather maps is relatively simple.
The lines, called isobars, which form concentric circles, outline the pressure zones. An H or an L will frequently be seen in the middle of the zones, designating a high- or low-pressure area. The numbers along the lines give you the barometric readings.
The squiggles, or isotherms, are simply lines connecting the same temperature over a wide area. For instance, if it is 50° Fahrenheit (10° Celsius) in Seattle, Washington; Butte, Montana; Chicago, Illinois; Cincinnati,
Ohio; and Charleston, South Carolina, a wavy line marked 50° will be drawn connecting those cities.
A number of these lines on a map will outline the temperatures and give you an idea of what may be coming, given the winds, storm systems, and pressure zones.
Isotherms show areas with the same air temperature. Isobars show areas with the same air pressure.