A/C breaker trips whenever ambient temp is high?

There may not be anything wrong with your RV, circuit breaker, or the A/C. In fact, the circuit breaker may just be doing its job correctly. The RV park may be experiencing a ultra high electrical load during those high temperatures that causes a drop in voltage. The lower the voltage, the higher the amps. And the circuit breaker trips when the amps go up.

The air conditioner does use more power at higher ambient temperatures. The breakers are also thermal trip devices (in general, for this situation--they also have a magnetic trip mode that's irrelevant here) and so when they are warmer they will trip a little sooner.

That's not to suggest that swapping the breaker is not a good idea; it's merely to give some reasons why it would trip when the temperature is higher but not when it's lower.

Filter is clean. It's just a ultra thin piece of foam.
Breaker is a dual 15/20 amp. The 20 amp is what trips.

If the ambient air is below 90-95 or so the A/C will run fine indefinitely and keep the trailer cool.

Need to find the easiest way to measure current draw without tearing too much apart. Hopefully the breaker box is easy to gain access.

Will try replacing the breaker as that should be easy and cheap to try.

My A/C circuit breaker started doing that. But was several years old at the time. Replaced the breaker and it never tripped again. But make sure the wire connections are tight. Loose connections can cause heating at the breaker and possibly lead to premature tripping.

Replace the breaker would be my start. A/C is on 20 amp breaker right?
Best to get your clap-on ammeter around the hot to measure actual amp draw.

Also try cleaning the filter, worked wonders for our a/c.

Loose connection in electrical system.
Get an amprobe to check for high load.
Check voltage