To find the amount of change in temperature, \( x \), every hour, we can use the equation based on the total drop in temperature over 5 hours:
\[ 5x = -12° \]
Now, we can solve for \( x \):
\[ x = \frac{-12°}{5} = -2.4° \]
So, the temperature decreased by \( 2.4° \) every hour.