This was the longest-lasting rain-caused rainbow I've ever seen. It was visible from mid-morning until the sun rose high enough to put it into the ground in the afternoon.
The weather in Glacier National Park, especially at higher altitudes, can be unpredictable. It is wise to have packable rain gear with you when hiking in this park. This storm was hanging over Glacier National Park but dissipating as it moved out the eastern side of the park - allowing full sun to shine through.
The foreground in this picture is a forest fire regrowth area showing fall color.