From SABR member David Kagan at The Hardball Times on March 9, 2018:
According to CBS Sports, MLB will require all 30 teams to keep yet-to-be-used baseballs in air-conditioned rooms this season. The point of this new regulation is to collect data to decide whether to require all the teams to use humidors to store balls in 2019. There are other side effects.
My prediction? The air conditioning will result in more home runs, not fewer. Summer humidity in places like the coasts, the South, and the northern Midwest is higher outside than in air-conditioned indoor spaces. The reverse is true in the desert such as Phoenix.
Humidity is a measure of the fraction of the air composed of water molecules. The higher the humidity, generally the more water is available to stick to surfaces; with lower humidity less water is available. The humidity in outside air is affected by temperature and atmospheric pressure. However, in controlled environments the humidity can be adjusted.
Read the full article here: https://www.fangraphs.com/tht/some-physics-of-humidors/
Originally published: March 16, 2018. Last Updated: March 16, 2018.