Many horse farms and facilities do not have unlimited space to store hay. Many of these farms and facilities do not have unlimited grazing, either, so they rely on hay to feed horses every day of the year.
According to Hay and Forage Grower and USDA reports, hay stocks on December 1, 2019, were about the same as 2017, and were up from 2018. However, these hay stocks varied greatly by state.
Hay and Forage Grower noted that, "In 2019, virtually all U.S. acreage, yield, and production metrics were at least marginally higher when compared to the previous year. The one exception was a slight reduction in total hay acres, which was driven by a smaller number of hay acres that were not alfalfa."
To find out more about hay availability and prices in your area, check with your county extension office.
Following are state-by-state charts from the USDA for hay stocks and alfalfa/alfalfa mix hay crops.