It seems there is not a lot of knowledge in this area and I am still scratching my head. I am now updating every 5 minutes and that is wrong! The issue I am getting is that when I send along rain for 24 hours and 1 hour every 5 minutes the weather-service is somehow adding it up incorrectly. I get 3.84 inches in the Opensprinkler GUI (System Status) when in real life I just had 0.685 inches over the last 24 hours. I will switch to updating once an hour and report back