@clayineuro - the other issue is does the runoff/overspray from the sprinklers freeze on the sidewalk, in the street or further down the street before it enters the storm drain. One can get a ticket for watering during freezing weather and creating a hazard or potentially be liable for damages caused when others (cars or people) slip on the ice created by watering during freezing conditions.
So it depends on how early the schedule is set to run. If the schedule is set to run when it is already daylight and will be warming up, then closer to 32 would be fine. If the schedule is set to run when there are a couple of hours until sunrise, then one might want to have some more room in there so that any water would be absorbed by the time any actual freezing temperatures occur.
Finally, how does the temperature at the weather station, assuming you don't have a PWS on premise, that the Rachio is looking at correlate to your actual temperature. Since Boulder was mentioned - if the Rachio is located up in the foothills west of town it might be actually cooler than WBU (Boulder airport).
So to paraphrase "your mileage may vary" - "the temperature you set for freeze skip may vary".