When the turkey thermometer “pops,” the little plastic or metal stem/button that usually sits almost flush with the white or clear base suddenly sticks up so it’s clearly raised above the surface of the bird.

What it looks like

  • Before it’s done, the button is mostly down, often with just a colored dot (commonly red) visible close to the skin.
  • When it pops, that colored pin springs upward and stays up, so you see a short little post sticking out instead of a flat dot.

What actually happens inside

  • Inside the timer there is a soft metal or wax that melts at a set temperature and releases a spring, which pushes the button up.
  • Many disposable turkey pop-up thermometers are calibrated around 170–180°F or higher, which often means the breast meat is already overcooked by the time it pops.

What you should do when it pops

  • Treat the pop-up as a rough visual cue only and always check doneness with a real meat thermometer in the thickest part of the breast and thigh (looking for at least 165°F and clear juices).
  • If the button never pops but your separate thermometer reads a safe temperature, rely on the thermometer reading rather than waiting for the built-in timer.

TL;DR: When the turkey thermometer pops, the little colored button that was nearly flat suddenly sticks up like a short peg, but use a proper meat thermometer to confirm doneness because pop-ups often signal the turkey is already overcooked.

Information gathered from public forums or data available on the internet and portrayed here.