Slows Bloons down even after they thaw out!
~ BTD 4 description
Makes the bloons so cold that they move slowly even after thawing out.
~ BTD 5 description

Permafrost is the second upgrade of the Ice Tower in BTD3 and BTD4. In BTD5, it's the 1st upgrade of the second path.

It allows Bloons to stay slow once they have been unfrozen. These are also one of the cheapest upgrades in BTD5, next to Sonic Boom, and Long Range Darts. If combined with Sabotage Supply Lines and glue it will make the red bloon as slow as a ZOMG.

BTD3 CostsEdit

  • Easy : $215
  • Medium: $255
  • Hard: $270

BTD4 CostsEdit

  • Easy : $85
  • Medium: $100
  • Hard: $110

BTD5 CostsEdit

  • Easy : $85
  • Medium: $100
  • Hard: $110
  • Impoppable: $120*

*Only available on Mobile/Steam