Copper Pipe Split, but its not winter?

We had a strange thing happen. Our copper pipe to our outside faucet has split. The weird part is that it has been working fine, and its now June. How did it split? Someone suggested that it started splitting during the winter, but that it didn't completely split until pressure was applied over and over again during the summer months. Is this possible? We never leave a hose connected during the winter months. The pipe is in an unfinished basement and no frost free faucet. Any ideas?