QUESTION:

I need to convert cooling degree days from 18°C baseline to 21°C how do I do it ?

ANSWER:

The weather tool uses a cooling baseline close to 20°C (the help file says 26°C, but I think it's closer to 20.5°C from my calculations). However, I am not aware of a way to change this baseline (perhaps a future option in the next Weather Tool?).

But changing your baseline from 18 to 21 C can still be done more or less manually. First, check out the equation the Square One web site is giving you. On the left of the screen, click on Climate Analysis --> Degree Days. There you'll find the equations you need to calculate your cooling degree days with the baseline you want.

An easy way to go about it would be to have all your data into a spreadsheet like Excel, and run a simple equation [IF(21-DBT>0,21-TDB,0] on a column, where DBT refers to your dry bulb temperature data for each hour. Then you can sum up your results. That will give you the annual total cooling degree hours. Divide that by 24 to get the cooling degree day.