If a little more time didn't resolve your hot water temperature problem, you may not have closed the bypass valve that diverts water around the water heater during winterization. This will cause cold water to mix with the hot water and affect the temperature and apparent capacity of the water heater.
Many designs use 3 valves to bypass the water heater during winterization. In the spring, the valves are placed in the normal use position, i.e., the two valves going to and from the water heater in the open position and the bypass valve in the closed position. Perhaps this is the problem.
2015 Wildcat 282 RKX
2011 F350 Lariat, 6.7 L. Diesel, 8 ft., SRW, Reese R20