Perhaps wearing only a thong and boots left Rihanna a little exposed to the elements: The pop singer still isn't feeling well and canceled Tuesday's (March 12) concert in Baltimore, after also missing out on Sunday's scheduled show in Boston.

After kicking off her [article id="1693402"]Diamonds Tour[/article] on Friday at Buffalo, New York's First Niagara Theater, [article id="1703385"]Rih Rih pulled out of Sunday's show[/article] at the TD Garden in Boston. Event promoter Live Nation issued a statement that cited the flu and laryngitis as the reasons Rihanna could not perform, adding that the show would be rescheduled.

Shortly thereafter, she took to Twitter, telling fans she was "embarrassed" about letting them down. "#Boston this is the hardest thing for me to deal with!" she wrote. "I feel like we've been waiting on this day forever, and I'm hurt that I let you down."

She hasn't tweeted since then, so there's no message yet for disappointed ticketholders in Baltimore.

[article id="1703389"]Chris Brown laughs off alleged Rihanna rant.[/article]

According to a review of the Buffalo show in the Buffalo News, the singer appeared in fine form on opening night. Though Rihanna was reportedly an hour late to take to the stage, the sold-out show featured impressive choreography from the singer, her eight dancers, two backup singers and four-piece band.

Stay tuned to MTV News for word on whether Rih will make her next scheduled tour stop at the Wells Fargo Center in Philadelphia on Thursday.

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