I live in the Middle East where the temperatures often are north of 50C in the summer.
As long as the humidity is low, the AC units perform very well and cool the apartment easily.
If relative humidity is high (usually we can tell this by the haze in the morning or when condensation start forming on glass windows), then the AC struggles to keep the house cool - but what's more interesting, it starts forming ice (on the cooling pipes) and this ice soon starts melting which leads to further issues that water starts leaking from the AC compressor unit.
My question therefore is, how can the ice formation be explained, and what is its relation to humidity and cooling?
In light of the comment below, I would like to clarify that I am not looking for a solution to the problem, I'm trying to understand the physics or the reasons behind it. I know that blasting some air through some of the drainage holes usually solves it; but I'm curious what is it specifically about humidity that makes this happen.