Hi Ray. Thanks for the comment. I figured there would be more involved in my request.
Here’s what I would think
I would say, if hi temp over the last 7 days is over 85, trigger “X program” to run every 3 days. Cancel run if rain sensor triggered in last 3 days.
If hi temp is less than 85, trigger “X program” to run every 7 days. Cancel run if rain sensor triggered in last 5 days.
Hi temperature is really what I think is important as even one day of high temperature will zap the water out of the grass. To be honest, I would want to play around with that temp a bit. I’m not sure if 85 is exactly the right temp. I think maybe closer to 90 makes more sense. But I’m sure that would all be manageable.