Violets grow best in temperatures of 19° to 23° C.
Temperatures below 17° C or above 26° C may kill your violet very quickly.
Violets appreciate being in relative humidity levels of 50-60%. Most areas of New Zealand have humidity levels that work well for African violets.
African violets dislike drafts.
Effect of temperature on variegated foliage:
Variegation in African violets is a genetic trait. Temperature variations cannot transform a violet with regular foliage into a variegated one. However, if a violet is a variety that has variegated leaves, the extent of variegation can be affected by external factors, such as temperature.
Cooler temperatures equal to more variegation (ie less green). This can look very cool, but reduces the plant’s ability to photosynthesise (only green parts are full of chlorophyll and are able to turn light energy into chemical energy).
Warmer temperatures equal to less variegation (ie more green). Sometimes variegated foliage can turn completely green (which still doesn’t change their genes, it is still a variegated variety).
NZ Violets 