Better yet... One in the Philippines where avg Humidity is 82%....????
Chalk and wood both react to humidity in much the same way in that they are both hygroscopic... Steps have to be taken in humid environments to keep either from gaining moisture.. Wood warps and moves when it gains too much moisture or loses too much if it was worked where it was humid but chalk wellll it's a little different....
Chalk works between 0% moisture content upto about 13% and it actually works better with some moisture until it contains too much moisture and then it will begin to miscue... We ship Great White at between 5-6% for that reason and to get it and keep it at that level we control the room and keep it at 40% humidity... It can go from 0% to 5% in about 24 hours after it comes out of our dryers..... Sooo hmmm 40% gets us to 5% and it works upto 13% so when would you worry...
Well back to the Philippines... At 82% humidity your chalk will get upto 16% moisture content in short order and since it sits on the rail more than it is used just a few gambling sessions with your own chalk would likely see that happen... A piece that has been sitting in the pool room likely has achieved that in just a day or so.... So what helps?.. Well believe it or not just limiting the airflow over and around the open surface.. Chalk and wood require air movement to gain or lose moisture... Keep it in a case, Use a cap or chalk vault... This will slow it down but you cannot stop it... One Efren Reyes, you might have heard of him, and a few more Pinoys have the habit of placing the chalk upside down... Yuppers.. This too will slow down the chalk wicking moisture and since pros generally have a reason for everything that they do since this is their living I am going to have to say I 1000% bet they do this because of humidity even if they don't know it......
Generally if your chalk gets too "wet" Simply tossing it in the oven for 30 minutes at 200F will dry it out unless it's saturated which may take an hour or more... You can actually use a moisture meter for wood on chalk if you wish to test yours and Corey Deuel was talking about starting to carry his in a Humidor LOL.......