Most indoor plants tolerate normal indoor temperature fluctuations. In general, foliage plants grow best between 70º and 80ºF (21º and 27ºC) during the day and between 60º and 68ºF (16º and 20ºC) at night. Most indoor flowering plants prefer the same day-time range but grow best at nighttime temperatures of 55º to 60ºF (13º to 16ºC). A cooler temperature at night is more desirable for plant growth. The lower night temperature promotes physiological recovery from moisture loss, intensifies flower color, and prolongs flower life.
Excessively low or high temperatures may cause spindly appearance (pdf), foliage damage (pdf), leaf or flower drop (pdf), and general plant decline. Avoid putting plants in areas with widely-fluctuating temperatures, such as on top of television sets. Move plants from window sills and doorways in cold months. A southern exposure is the warmest; eastern and western exposures are less warm; and a northern exposure is the coolest.
Temperature requirements of selected house plants, Table 11.2 (pdf) in California Master Gardener Handbook. UC. Buy Publication