Calculates mean temperature of the period with the highest precipitation sum.
bio08_fast(tperiod, pperiod_max_idx, period_length, cell)Matrix with "bio08", "cell".
Matrix of temperature period sums (output from `var_periods`).
Vector indicating the index (1-based) of the wettest period for each row.
Integer. Number of units per period.
Vector of original cell IDs.