Boston and nonprofit Mass Poetry have partnered on what they call "Raining Poetry." It's sidewalk verse by local poets—with a twist. Per Mass Poetry: "Using a biodegradable water-repellent spray and stencils made by local artists, the city's Mural Crew is setting out to place poems throughout the streets of Boston. The spray vanishes once dry, so the poems are invisible—until it rains. Once wet, the area around the poems will darken, and Bostonians will be treated to short poems as they walk around the city."

The phenomenon is expected to hold for at least a month. Here's where you can see the poems the next time it pours. (All photos are from Mass Poetry and h/t CBS Boston.)