On my gen 2 my PWS is used for the actual rainfall (after the fact). Somehow the gen 2 can forecast, from my PWS, and historical records, the forecasted rainfall going forward, but once a day is over it updates the rainfall with the actual rainfall from my PWS. Having a PWS on my property makes the Rachio system work much better. I have read that the main difference in gen 2 and 3 is that the 3 does weather from many more weather stations, and can average several stations, but nothing beats having the info from a PWS on your property.
