Yes I can. I tried to simplify the flows a bit. If it starts or stops raining, the countdown timer will reset. After 36 hours (129.600 sec) the timer will end. So it will end when it was dry the last 36 hours or it was raining for the last 36 hours (which is very rare, so I think it can be defined this way).
If the timer is empty at 20:00 and it was warmer than 15 degrees that day, then start watering the garden. Please find the examples below: