Temperature makes salt crystals form faster or slower. Salt dissolves faster in warm water than in cold water, so colder water will make for more crystals.

There are many types of crystals, but in evaporation crystals, temperature is very important. Warmer temperatures allow the molecules to move faster and will make the crystal form faster. Humidity also increases the rate of crystal formation for evaporation crystals. If the temperature is higher, evaporation rate will be higher, so more crystals will be started but they won’t have time to grow as large.