According to North Carolina State University, hummingbird feeders should be outside when the birds arrive. The time of arrival varies across the country. Hummingbirds could start coming in January or February in the lower south or in April or May in the north.
North Carolina State University reports that leaving feeders outside all year does not keep hummingbirds from migrating. Some hummingbirds don't leave some parts of the country during winter, including the west coast, the southwest and a few areas in the southeast.
Leaving feeders out all year could let you see some hummingbirds even in winter. However, the feeders require more maintenance to keep the sugar solution from freezing, according to North Carolina State University.