To find the average temperature change per hour caused by Tropical Storm Cecil, we can divide the total temperature change by the total number of hours.
Given:
- Total temperature change = -18 degrees
- Total time = 12 hours
We can use the formula: \[ \text{Average temperature change per hour} = \frac{\text{Total temperature change}}{\text{Total time}} \]
Plugging in the values: \[ \text{Average temperature change per hour} = \frac{-18}{12} \]
Calculating that gives: \[ \text{Average temperature change per hour} = -1.5 \text{ degrees per hour} \]
Therefore, rounding to the nearest tenth, the average temperature change each hour is -1.5 degrees.
So, the correct answer is -1.5.