I noticed my issue for the first time after I wanted to enable it after the winter. We had a “good” winter with enough regular rainfall that allowed me to disable irrigation.
Initially I had thought that each time it needs to check the weather that it will get the wi-fi dongle out of sleep mode and that it should be sufficient.
The same would go for NTP. I’m fairly confident that I have enabled NTP as far as I understand the Pi does not have it’s own clock and I’m running on GMT+2.
What might have thrown it off is that I set my location by clicking on the weather area on the top to the left. This took me to a map where I could pick my location. So I was not using Weather Underground. I have since changed to Weather Underground as I discovered that I actually had a WU API Key.
I’m not sure how often it does these checks and whether it is frequent enough. It usually also only happened when there was a day where no irrigation happened. So maybe it only checks weather and time when there is irrigation scheduled for the day.
Anyway, I now had to change my stations due to water restrictions. (Thus the quoted “good” above.) So I now run a station every day in order to stay within the allowable hours as I don’t like irrigating at night as it apparently causes issues for roses and sometimes grass as well.
Troubleshooting this is going to be an issue as you’ll have to write a little utility that sends emails at regular interval and then keeps a log. It should then increment the interval between emails after each day it was successfully at sending emails and doing an on-line check of some sorts. Then when it eventually breaks after a few months you should have the optimal interval to poll in order to keep the wi-fi alive.
The one thing I will have to check first is to see whether I did set the dongle to prevent it from sleeping after I rebuilt my SD card to the unified firmware. https://www.raspberrypi.org/forums/viewtopic.php?t=61665
Have any of you tried the steps above already?