Don't put cold cast iron on a hot burner.

Yes, it can warp.

The issue is thermal shock. Cast iron heats unevenly when a cold pan hits a hot burner. The part in direct contact expands faster than the rest, and that sudden stress can bend the metal. Once it’s warped, it wobbles on the stove and doesn’t make good contact—ruins the cooking experience.

That said, it’s not guaranteed to happen every time. Thicker pans (like vintage ones) handle it better. The worst offenders are thin, cheap modern pans and rapid high heat. Induction burners are especially aggressive with this because the heating is so intense and localized.

Best habit: let the pan warm up with the burner. Start on medium, then crank it. Or at least let a cold pan sit on the counter for a few minutes before lighting the fire.

Your pan will thank you.