Why do snow-fed tributaries of the Yukon River reach peak flow in June?

Snow-fed tributaries of the Yukon River reach their flood peak in June primarily due to the seasonal melting of accumulated winter snowpack in the Mackenzie Mountains and surrounding regions as temperatures rise during the spring and early summer.1

In contrast, streams fed by glaciers, such as the White River, experience their greatest runoff later in the season, typically in July, because the melting of glacial ice requires more sustained heat and time than the melting of seasonal snow. Following these peak runoff periods, the Yukon River generally becomes a shallow braided stream, as summer precipitation within the basin is relatively low.1