at what temp does salt stop melting ice

Salt never has one single “off switch,” but as a rule of thumb plain road salt (sodium chloride) becomes barely effective around about 10–15 °F (about −9 to −12 °C), and is essentially “done” somewhere below about 0 °F (around −18 °C).

Quick Scoop

• For normal road/rock salt (sodium chloride):
  • Works well just below freezing (32 °F / 0 °C).

* Melts much less ice by 20 °F (−6 °C).

* Is _barely_ working by about 10 °F (−12 °C) and below.

• Many winter maintenance guides treat about 10 °F (−12 °C) as the practical point where “salt stops melting ice” in any useful way.

• Other de‑icing salts go lower:
  • Magnesium chloride: effective to roughly −5 °F to 5 °F (−15 °C).

* Calcium chloride: can keep melting ice down to roughly −13 °F to −13 °F and even around −13 to −25 °C in some products.

Why it seems to “stop”

Salt works by dissolving into a thin film of water and lowering its freezing point, creating salty brine that can stay liquid below 32 °F.

When it gets very cold, there just isn’t enough liquid water on the ice surface to dissolve the salt and form that brine, so the reaction slows to almost nothing and looks like the salt has stopped working.

So if you’re thinking “at what temp does salt stop melting ice” for everyday driveway or road salt, the practical answer most people use is: around 10 °F (−12 °C), it’s barely melting anything, and colder than that it’s effectively not working.

TL;DR: For typical rock/road salt, expect useful melting only above about 10 °F (−12 °C); below that it quickly becomes practically ineffective unless you switch to a colder‑weather product like calcium chloride.

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