The man of the hour – toting an umbrella – greeted fans lined up outside of Reed Space on Orchard St., where a pop-up shop featuring photography and merchandise has been assembled for the week.
Mayer – who donned a t-shirt featuring lyrics to second single "Queen of California" once he spotted it for sale inside – mingled with friends, family and industry pals before settling down in the back corner with a pile of Sharpies, ready to meet the crowd gathered outside.
Admitted five at a time, hundreds of fans had their chance to greet the seven-time Grammy winner, who doled out hugs, posed for photos and signed everything from CD booklets to guitars.
"He looked like he was having a great time interacting with fans," an onlooker tells PEOPLE. "Especially since he won't be able to tour."
The Born and Raised Store will remain open through May 27, with a portion of proceeds benefiting NCIRE, the veterans health research institute Mayer supports.
– Sarah Michaud and Sara Hammel