From June to December, the average rainfall values are as follows:
- June: 0.2 inches
- July: 0.45 inches
- August: 0.55 inches
- September: 0.7 inches
- October: 1.6 inches
- November: 2.4 inches
- December: 3.2 inches
Analyzing these values, we can see that the average rainfall increases from 0.2 inches in June to 3.2 inches in December.
Therefore, the correct response is:
the average rainfall increases.