The temperature that is too cold for plants varies depending on the type of plant. However, there are some general guidelines to follow. Most houseplants living outside for the summer need to be brought back indoors before overnight temperatures dip below 45 degrees Fahrenheit. Some succulents may suffer harm even before this, so bring them inside when temperatures drop below 60 degrees Fahrenheit. For most plants, its best to wait until nighttime temperatures are consistently above 50 degrees Fahrenheit. When it comes to heat-loving, fragile plants, you may want to wait even longer until its warmer. According to the Department of Plant and Soil Science at the University of Vermont, it’s time to bring houseplants inside when temperatures drop below 50 degrees Fahrenheit. Some plants can survive outside even when temperatures hit freezing, while others need to be brought indoors when temperatures reach the mid-40s Fahrenheit. Its important to note that even before temperatures drop enough for a plant to be damaged from cold, the plant may stop growing as vigorously as it did in warmer weather.