Source Hoosier Tire:
https://www.hoosiertire.com/faqdrag.htm
TIRE STORAGE
The useful life of a tire, whether mounted or dismounted, is directly affected by storage conditions. Tires should always be stored indoors in a dark, cool, dry room.
DO
1 Remove the tires from the vehicle.
2. Remove the air from the tires and store them on their side in a cool/dark/dry environment.
3. Place tires in a black plastic bag when stored during the "off-season".
4. Make sure the temperature range in the storage location is between 40-90 degrees Fahrenheit.
DON'T
1. Don't store tires in direct sunlight or near electric motors. (Electric motors emit small amounts of ozone.) Tires need to be protected from light, especially sunlight. Light causes ultraviolet damage by breaking down the rubber compounds. The storeroom should not contain electrical welding or any other equipment that could produce ozone.
2. Don't apply any chemical treatments to Hoosier tires. (It's not necessary and may actually damage the integrity of the tire by breaking down the rubber properties of the tire.) Tires must not be allowed to come in contact with oils, greases, solvents, or other petroleum products that cause rubber to soften or deteriorate.
3. Don't store tires in sub-freezing temperatures for any length of time. (The rubber can freeze and may crack as a result.)