What are the chances of being able to tell my baby's gender at my 13 week ultrasound?

At my upcoming ultrasound I'll be 13 weeks and 3 days then. Just wondering the chances of being able to see the baby's gender then. Is it even possible? I've heard it's possible that early if the baby cooperates. I just don't want to get my hopes up. My sister found out at 15 weeks. But I know most people don't get to find out until closer to 19 weeks. Just wondering if anyone on here has found out as early as 13 weeks or know of someone who has?