Most plants tolerate normal temperature fluctuations. In general, foliage plants grow best between 70 degrees and 80 degrees F. during the day and between 60 degrees to 68 degrees F. at night. Most flowering plants prefer the same daytime temperature range, but grow best when nighttime temperatures range from 55 degrees to 60 degrees F. Lower nighttime temperatures help the plant: recover from moisture loss, intensify flower color and prolong flower life. Excessively low or high temperatures may cause: plant stress, inhibit growth, or promote a spindly appearance and foliage damage or drop. Cool nighttime temperatures are actually more desirable for plant growth than high temperatures.
A good rule of thumb is to keep nighttime temperatures 10 to 15 degrees lower than daytime temperatures.