Based on the student’s observations, the best explanation for the weather changes is "A cold front moved into the area."
Here's the reasoning:
- Day 1: Sunny and warm - This likely indicates a warm air mass.
- Day 2: Cloudy and rainy - This suggests the presence of moisture, indicating that a front may be approaching.
- Day 3: Drop in temperature - A drop in temperature typically follows a cold front where cold air mass pushes out the warm air.
- Day 4: Clear skies and cold temperatures - Following a cold front, clear skies are common as the cold, dense air moves in and stabilizes the atmosphere.
Thus, the observation of a drop in temperature and clear skies in conjunction with the initial warm conditions strongly suggests that a cold front moved into the area, causing these changes.