AceShowbiz -

Katy Perry is sorry for having to postpone two of her California Dream shows, one in Chicago and the other in St. Paul, this week. The "Last Friday Night (T.G.I.F)" singer was forced to cancel her concerts in the two cities due to "an attack of food poisoning leading to severe dehydration."

She stated on her official website, "I apologize to my fans in Chicago and the Twin Cities for not being able to perform this weekend, but I am going to return in a few weeks to give them the very best show ever!" Sharing the same sentiment to her Twitter followers, she wrote, "Chicago and St. Paul - I'm so sorry to have to postpone today and tomorrow's shows."

She was supposed to perform at Chicago's Allstate Center on July 8, and at St. Paul's Xcel Energy Center the next day, but has now moved the dates to August 21 and 23 in the same venues respectively. "All tickets will be honored at the new dates, or refunds can be processed at the point of purchase," it was announced by the promoter.

The concert cancellation came just a week after Katy announced one additional date for the South American leg of the lengthy tour. Already mapping two Brazil gigs, she added another concert at Estadio GEBA in Buenos Aires for September 27.

Katy Perry is not the only singer who took timeout from her tour due to illness. Just last weekend, fellow artist Taylor Swift delayed at least four of her North American concerts due to suffering from Bronchitis. A few weeks prior, it was Adele who canceled remaining dates of her tour in the country due to laryngitis.