The data is freely available from the Climate Change Service [1] which has a nice API but download speeds can be a bit slow. You'll have to sign up for this.
NCAR's Research Data Archive [2] provides some of the data (as pre-generated NetCDF files) but at higher download speeds. No signup necessary.
It's not super well documented but I hosted the Python scripts I used to download the data on the accompanying GitHub repository [3].