Supposedly the type of mold that grows on fermenting saurkraut isn't harmful unless a person would be allergic to it...still... I don't like seeing it, which is why I stopped making pickles and sauerkraut in the hot months. We don't have air-conditioning and I just wait until fall to start up again when things cool down.
One time a train was leaking some gas across the river from us and we were supposed to keep out windows shut for several days in June or July, I think it was, a few years back, and my beautiful, fermenting pickles got so nasty I couldn't even think about trying to save them... our house got ridiculously hot all shut up like that without air conditioning. Now I just wait until fall to ferment because I don't like dealing with the idea of mold, even though, as I said, it's supposedly not a harmful variety.