Best friends Hannah, Jentry, Paige, and Sally take an epic road trip the summer before their junior year of college at Brigham Young University. While traveling through Oregon, they bury a time capsule with predictions for their future, which includes always being best friends. They make plans to return on their fortieth birthday to dig it up and see how many predictions came true. Throughout the next decades, the four friends are a constant support in each other's lives. But when Hannah leaves the Mormon church, not everyone is happy, causing hurt feelings and strained relationships.

As their forty-seventh birthday approaches, Sally is able to convince everyone to dig up the long-buried time capsule. Will reading their old hopes for the future be enough to heal the hurt of the past? Will they be able to come back together and support each other through the hardest trial yet?

Set in Oregon, Utah, and Washington, Summer Rain tackles themes such as adoption, divorce, domestic abuse, faith transition and infertility.