Q.I just got a hydrangea and want to plant in the yard, but it says only in the fall. Can I NOT plant in my yard if I plant NOW since
the weather is super cold still? If you look on weather for MO I live in STL area you will see how crazy our weather is.

If it has leaves, keep your hydrangea inside until after your frost free date in May. At that time, harden it off over a week then plant it outdoors. Water weekly if rainfall is less than an inch per week all summer and fall. When temps are over 90, it may need water twice weekly. If your hydrangea is "bare root" it needs different care. Bare root plants are often shipped in fall for planting right away. However, don't try to plant while the soil is still very wet from winter snow and rain. I've included links to articles that should help.
https://www.gardeningknowhow.com/garden-how-to/propagation/propgen/bare-root-planting.htm
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea