We have a fairly extensive home auto setup at our home. Included is a Netatmo Rain Gauge. All APIed to our RaspberryPi running openhab.

One of the parameters we are able to pull from the api is accumulated rain within 24 hours, in mm.

Rather then relying on Rachios (we use their sprinkler IP bridge) "app" to schedule watering, I would rather roll our own and have more control over when the sprinklers go off.

I am not sure in mm what is considered a 'sufficient' watering for our grass. I understand this can vary, but I have no idea what a starting point would even be.


It depends a lot about the type (species) in your grass. I estimate that there is more than a factor 20 between ideal dry grass and ideal wet grass. Unfortunately being above 3-5 time the ideal value could ruin your grass. But probably you have drainage, so possibly it is less sensitive to overwatering.

So I would change approach. Try (maybe looking at the raining per day on raining days), and decreasing the value a lot. When grass start turning yellowish, you should increase water (no changes? look fertilizers).

A would stay on the lower part or watering, to force better roots (assuming you want green grass and walking in it).

The influencing factors:

  • evaporation from leaves (so sun, temperature [at soil] and humidity).
  • grass species (but it is indirect from first point) and in minor manner:
  • mow grass (just after mowing), non-sharp blades
  • grass grow (seasonal)
  • soil (e.g. sand)

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