What weather phenomenon often occurs at cold fronts?

The presence of thunderstorms at cold fronts is closely linked to the dynamics of how cold air interacts with warm, moist air. When a cold front moves in, it displaces the warmer air ahead of it, forcing that air upward rapidly. This abrupt lifting of warm air leads to the development of cumulonimbus clouds, which are the towering clouds associated with thunderstorms.

As the warm air rises, it cools and condenses, releasing latent heat which further fuels the storm development. The combination of instability, moisture, and lift can result in significant storm activity, including heavy rain, lightning, and sometimes severe weather events such as hail and tornadoes. This is why thunderstorms are a common and notable phenomenon associated with cold fronts, making it the correct answer to the question.

Fog, snow, and heat waves, while they can occur in various weather contexts, are not typical phenomena directly associated with the rapid and dynamic conditions created by cold fronts. Fog tends to develop in more stable atmospheric conditions, while snow is often associated with more prolonged low-pressure systems rather than the rapid change brought by a cold front. Heat waves are characterized by prolonged periods of excessive heat and are not relevant to the dynamic climate changes associated with cold fronts.