I have a unique application which I have adapted the controller to achieve, however it could be better accomodated via a firmware/software implementation. I am using the controller to water a Florida flat concrete roof to provide evaporative temperature reduction. Implementation: I wired the outputs of the 8 zones to a single valve. Each zone is set to start at 1 hour increments beginning at 10:45 AM and run for 13 minutes each. This evaporative cooling reduces the inside ceiling temperature by 20 degrees (eg. reduction from 118 degrees to about 98 degrees. Without the evaporative cooling, the concrete roof acted as a heat sink which stored and radiated heat well after the sun went down. Now the air conditioner can keep the room comfortable. FYI, this is a interim and temporary solution for the occasional summer Florida guests staying at an apartment which is normally occupied only during the winter (eg bearable without A/C) months.
I have no answer for you but I’m stuck on a concrete roof!?
Ingenious way to use the Rachio. Wonder what the crop coefficient of concrete is. 
But seriously, I’ll bet that you could toy with it enough to allow Rachio to control the “sprinklers” based on temperature so that you aren’t wasting more water than you need to.
Seems like this would compound an already bad mold situation. Could you install a window air conditioner instead?
I already have 2 window a/c’s cranking for their 2 week visit, so internal moisture is o.k. Note that without the a/c and without the roof sprinkler the inside of the roof/ceiling would reach about 110 degrees and hold that temperature well after sunset. It was like a large heat sink radiating heat into the room from above. With the sprinkler, the inside ceiling stays about 20 degrees cooler. Old concrete block homes in Florida were built with gravel and tar flat roofs for the purpose of evaporative cooling. And of course the ultimate hurricane resistant structure.