McGraw's wife, singer Faith Hill, emerged from backstage to address the crowd, telling fans that her husband was "super dehydrated". "I apologise, but I made the decision that he can not come back out on stage", Hill said.
A spokesperson says McGraw will be "fine".
Local entertainment journalist Eddie Rowley tweeted that a publicist said McGraw was treated on site and will be fine.
Fans posted messages of support and well wishes on McGraw's social media. After her announcement Hill performed a gospel song called "What a Friend We Have in Jesus" and ended the show.
The performer was here as part of the Country to Country festival now underway. Hill and McGraw were the headliners, along with Little Big Town and Kacey Musgraves. The couple will be starting the latest edition of their Soul2Soul tours following last year's release of The Rest of Your Life. McGraw wrote on Twitter, tagging other major retailers including Walmart, Kroger and LL Bean.
McGraw has been in the news lately for his stance in favor of gun control. "A true hero who lost his life protecting the children", McGraw tweered.
Tim and Faith have been married since 1996 and share three daughters.