The average relative humidity in Amritsar, India, one of the biggest centers for chess set manufacture is 65%
https://www.currentresults.com/Weather/India/humidity-annual.php
From the House of Stanton site:
The recommended temperature and humidity levels for solid wood products are as follows: Winter Temperature 65-70 degrees F Relative humidity 35%-45%
Summer Temperature 70-75 degrees F Relative humidity 55%-65%
TEMPERATURE AND HUMIDITY – Wood is a hygroscopic material, which means that it readily transfers water with the environment in which it is stored. If a wood product (such as a chess piece or chess board) is kept in an area of high moisture, the wood will absorb water from the air, causing the wood to swell. If a wood product is kept in an area of low moisture (dry), the wood will lose water to the dry air, causing the formation of structural cracks and lifting veneers and inlays (chess boards). While the moisture levels in the air vary throughout the year, the most dangerous time for your new wood chess product is during the winter. This is because the naturally dry air that is further dried by your HVAC unit as it heats up your home (by heating up the air). Most of us have experienced dried or cracks knuckles and lips during the winter time. This is caused by the air being too dry, and that dry air basically steals water from your skin. The same process happens to your wood product, it loses water to the dry air. But, unlike your lips, once a crack has developed in a piece of wood, there is no way to repair it to a “like new state.” You can purchase inexpensive humidity and temperature sensors on the internet and at home improvement stores for less than $10. If you nd that the relatively humidity of your surroundings does not fall within the ranges dened above, we strongly recommend that you purchase a humidier (for low humidity) or dehumidier (for high humidity). We at the House of Staunton use multiple humidiers during the winter time in our luxury chess piece storage room to maintain proper moisture levels.
Pretty soon your whole set is gonna look like these guys
I do that with my Revell models. 
Hello all,
I received this set brand new a little over a month ago from India. The pieces in the pictures are made of boxwood. When I received them, they were not this way... they were polished smooth, I am 100% certain. Within 40 days, these two pieces (one pawn and one rook) have begun to "wrinkle".
Does anyone know what could be causing this? My guess is that the wood was not properly dried before carving/turning, and now that the wood is drying, it is beginning to look like a raisin. I'm not an expert on wood, but these pieces are kept in 40 to 50% relative humidity (I have acoustic guitars so I keep hygrometers in several places in the house) and it's difficult for me to believe they would dry out.
Someone educate me please. Thanks