This is what happens to an outdoor balloon arch when it really rains. This arch was built with the aeropole system and as water is heavy the poles are not built to carry that much weight.
There is a simple solution, use less poles. If you use 4 or 5 poles the arch is substantially stronger, the more poles you use the more flexible and bendy the system becomes.
This was an excessivly wet day as in it absolutely hammered it down. On most occasions the system can handle it and usually dries off between intermittent downpours.
What happens when it rains?