weighted_temperature_sum: Create a weighted temperature sum
Description
A temperature sum is constructed by summing the average daily temperature
for each day, but applying a weight factor of 0.5 for January and 0.75 for
February.
vector Daily average temperatures in degree Celsius.
negative
boolean Whether to include negative temperature values in
the summation. By default, negative values are set to 0, meaning that
the temperature sum is monotonically increasing.