What temperature does it have to be to freeze water with salt added?

Answer 1

Zero deg. F.*

The original definition of zero fahrenheit, centuries ago was "the lowest temperature achievable in a laboratory using salt (NaCl) and ice or snow". Modern science has shown that a saturated salt solution actually freezes at a few degrees below zero. For practical purposes: melting snow on roads and walks or making ice cream, one can use zero F., -18C. Sea, ocean water freezes at 28 deg. F. ,-2 deg. C.

Answer 2

Salt lowers the freezing point of water, so the temperature at which saltwater freezes depends on the concentration of salt. A typical concentration of salt in seawater (around 3.5% salt by weight) can freeze at a lower temperature than pure water, typically around -2°C (28°F) to -6°C (21°F).