How long in the summer should I expect my calla lilies to continue to bloom?
How Long Do Calla Lilies Bloom?
A calla lily variety may flower for from 4 - 10 weeks, depending on the specifics of each one. Also, they bloom at different times, so you can plant several varieties to have flowers from late spring all the way through summer. This article will tell you more about growing them: https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/growing-calla-lilies-and-care-of-calla-lilies.htm
By the way, to learn your zone, you can go here: https://www.gardeningknowhow.com/planting-zones/