The kelvin scale is the standard absolute thermodynamic temperature scale.
Therefore, this question is simply asking you to convert the degree fahrenheit into degree kelvin.
The formula used to convert between kelvin and fahrenheit is as follows:
T(K) = (T(°F) + 459.67) × 5/9
We will substitute in this equation with T(F)=-13 and calculate T(K) as follows:
t(K) = (-13 + 459.67) x 5/9 = 248.15 K
Based on this, the previous sentence can be written using absolute value of the number as follows:
The temperature at night reached 248.15 K.