Present-day Coldwater, Maine, and 1565 Loire Valley, France
Hush, Hush uses a damp, foggy northern U.S. small town as the setting for its fantasy. Coldwater is fictional, but nevertheless, the creepy, rainy, gray setting is perfect for other worldly creatures and things that go bump in the night. As Nora puts it when she's describing the 18th-century farmhouse she lives in with her mother:
I sometimes wonder if the original builder realized that out of all the plots of land available, he chose to construct the house in the eye of a mysterious atmospheric inversion that seems to suck all the fog off Maine's coast and transplant it into our yard. The house was at this moment veiled by gloom that resembled escaped and wandering spirits. (2.1)
What's more, Coldwater is a border setting. Maine is situated at the upper extreme of the U.S.'s limits, and Coldwater is also near the coast, on the border between land and ocean. Here's a fancy-sounding explanation of why this matters: Borders are liminal spaces. That means they're transitional settings, thresholds, outskirts that allow for crossovers not possible in other places. In Hush, Hush, there are slippages between heaven and earth, reality and fantasy, good and evil. The setting, then, reflects the movement between the supernatural and real and the blending of the two that goes in the book.
Here's an extra bonus observation about borders for you to chew on: The restaurant where Patch works and where Vee and Nora go a couple of times in the book is called the Borderline.
The Loire Valley is a 170-mile stretch along the middle section of the Loire River known for its lush vineyards and orchards as well as its stunning architecture. The fantastic folks over at Lonely Planet describe the scene as follows:
Spanning the course of history from medieval to Renaissance and beyond, these monumental masterpieces evoke the brilliance of a bygone era. (Source.)
The region is steeped in romance, history, and Eden-like gardens. This setting gives the novel a sense of grandeur and suggests that not only will there be romance, there will be characters locked in a centuries-old struggle.
Perhaps most importantly, "renaissance" translates from French to English as "rebirth" (source). So this opening setting is a subtle hint that some of our characters will be exploring their identities and going through changes. Only the few pages of the prologue take place in the Loire Valley, but the atmosphere introduced in these pages hangs over the entire book.