Your light will be ok at 90% but your plants won't lol and for the love of Judith NEVER take your diffuser of in a room with high humidity,you want to do that in as dry a place as poss.....if you do it in 90% RH room moisture may get trapped inside. These lights have several gaskets there is one on the actual module one on the outside of the light that the diffuser sits on and one on the diffuser itself, it difficult to get moisture in there but also to get it out if any gets trapped inside.