This year’s event brings 18 new back, side and front yards and even an open field of lupines throughout the four participating neighborhoods. (Photo: N. Patterson)

The rain has stopped and the forecast is for a sunny, 78-degree Sunday — perfect for the self-guided “Secret Gardens of Cambridge” tour.

This year’s event brings 18 new back, side and front yards and even an open field of lupines throughout the four participating neighborhoods, while the rest of the more than two dozen yards on the tour may reveal lessons through the changes spotted by those who went on the most recent tour, two years ago.

The addition of gardens “provides an opportunity to explore the city, discover new spaces and give exposure to new ideas, designs and gardening tips,” said Martha Osler, secretary of the Friends of the Cambridge Public Library.

“Secret Gardens” tour is the single biggest fundraiser for the library, usually resulting in more than $10,000 toward buying books, paying for programs and bringing in authors for readings, Osler said.

Access to the event, running from 10 a.m. to 4 p.m. Sunday, requires a ticket — $25 for the general public or $20 for members of the Friends of the Cambridge Public Library buying at the Cambridge Main Library, 449 Broadway. All branches of the library sell regular-priced tickets, as do Bonny’s Garden Center, Dickson Brothers Hardware, Harvard Book Store, Nomad, Pemberton Farms, Porter Square Books and Rodney’s Bookstore.

For information, send e-mail to [email protected].