I have changed my apilio.io and IFTTT applets to reschedule the watering program in case of a rainy day with sufficient rainfall. Instead of setting a custom rain delay time, which stops the watering for e.g. 24 hours, I changed the program to restart the following day. The API command used for this purpose is:
(Modify existing program, program enabled, use weather adjustment, no restriction, interval day schedule, fixed start time type, runs every 2 days, starting from tomorrow, start at 7:00 AM and the running stations are 1st station – 30 minutes, 2nd station – 30 minutes, 3rd station -30 minutes, program name is Summer2018)
This seems to be a more realistic approach, as it avoids non-watering periods of more than two days, if there are no further rainy days with ample rainfall. Unfortunately there exists no simple API command to delay (reschedule) a watering program by one day, which makes it necessary to use the Change Program Data command with all parameters for this purpose.
Again, I carefully have to look at the changes made to my automated sprinkler system. But for the time beeing it looks very promising.