On a conference call today, President Obama reached out to supporters who will no longer be able to attend his convention speech.

"We can't let a little thunder and lightning get us down," Obama said. "We're going to have to roll with it."

Weather forced the event to be moved from the Bank of America Stadium to the much smaller Time Warner Cable Arena, meaning supporters who got "community credentials" to attend have been shut out. Many were volunteers who won their tickets after logging nine hours of campaign work.

Obama said he regretted having to move the speech but that the risk of a severe storm was too great. 

 "I know it's disappointing," he said, but "the problem was a safety issue. I could not ask you -- our volunteers, our law enforcement, first responders -- to subject themselves to the risk of severe thunderstorms."

The president encouraged listeners to attend local watch parties, saying he needed their support and enthusiasm more than ever. "I really need your help, guys," he said. "Nothing is more powerful than the work that you guys do. Nothing is more powerful than your voices calling for change."