It seems that, even though the weather data is available throughout the day, that zones without sensors only use the forecast high and low.

This is insufficient to correctly adjust for the amount of watering required.

For example, today is 7 degrees C up to 36.

Whisperer zones average the temp at 26C while non-Whisperer zone calculate the average at 22C.

On these extremely hot days, the non-whisperer zones are under-watering much more than the Whisperer zones.

Also note that even the zones with Whisperers always under-water and needs custom programs or manual intervention.

This finally explains to me why zones are always under-watered.

Can the system please use multiple day readings for non-Whisperer zones and PLEASE provide more watering?