We report the first cases of simultaneous double brooding known for Calliope Hummingbird (Stellula calliope) and Rufous Hummingbird (Selasphorus rufus) from observations of two females in Montana. Each female laid two eggs and started incubating while feeding large young in a nearby nest, and each successfully fledged young from both nesting attempts. Simultaneous multiple nests have been documented for five other hummingbird species that breed north of Mexico, suggesting the behavior is widespread in the family outside the tropics. Factors that might allow rapid renesting in temperate species include young that begin to feed themselves within a week after fledging, and longer day length that allows more time for females to forage than would be available in the tropics.