At what temperature does salt become ineffective in melting snow and ice?

The minimum practical application range for salt is a pavement temperature of 15-20 degrees F and above. While salt will melt snow and ice down to a pavement temperature of -6 degrees F, it can melt over five times as much ice at 30 degrees F as at 20 degrees F. Thus the effectiveness of salt is sensitive to small differences in pavement temperature.