Jim, I just put up the Watering Index last night! I've had it running for a few months now but wanted to make sure is was working properly. Just to give credit where credit is due I did not create this feature, I thank Chris at SLOWeather.com for creating this script and allowing me to use it.  I have lawns in both my front & back yards I have have use this index to conserve water and I have expirenced no ill effects.  One think to remember, not for you because you live in 1000 Palms, is wind effects Evapotraspiration. So this index will be the most accrurate in the north side of the valley. And not the east end because the dew point values then to be higher than the west end.  Because of these variences I still have to find tune the headers.