The dry line is a weather feature that is most common during the spring and summer months in the plains region. It is unique to the plains region, specifically western Texas, Oklahoma, and Kansas because of their positions between the mountains and desert and the Gulf of Mexico. A dry line sets up when the dry air from the mountains and the desert out west line up next to the moisture filled air from the Gulf of Mexico in the east. This drastically different air creates a tight dew point temperature gradient usually in western Kansas.
As the two air masses collide, the dry air sits on top of the moist air as it is pushed east usually by a low pressure system to the north. This results in instability and produces a thunderstorm.
The difference between a dryline and a cold front is the temperature change. Most of the time temperatures behind the cold front will drop about 10 degrees. This is not the case with a dry line.