Final answer:
A significant temperature drop of 20 degrees is indicative of a cold front, which involves a cooler air mass replacing a warmer one, often causing abrupt weather changes.
Step-by-step explanation:
When the temperature dropped 20 degrees on average, the type of front experienced was likely a cold front. A cold front occurs when a cooler air mass moves in and replaces a warmer air mass, leading to a significant drop in temperature. This is typically associated with a swift change in weather conditions, which can include a sharp decrease in temperature, as well as the possibility of thunderstorms or other severe weather events. Cold fronts are often more dramatic and fast-moving than warm fronts, which generally bring more gradual changes in temperature and weather conditions.