Miguel woke up and found the temperature outside was 7°C . When he went to bed that night, the temperature was −8°C . What was the magnitude of the temperature change?

To find the magnitude of the temperature change, we can use the formula:

\[
\text{Temperature Change} = |\text{Final Temperature} - \text{Initial Temperature}|
\]

Given:
- Final Temperature = 7°C
- Initial Temperature = -8°C

Substituting these values into the formula gives:

\[
\text{Temperature Change} = |7°C - (-8°C)| = |7°C + 8°C| = |15°C| = 15°C
\]

Thus, the magnitude of the temperature change is \( \boxed{15} \)°C.