The season for moving your succulent and tropical plants back inside for the winter has nearly arrived. Some general numbers that we use to determine when to bring plants in are: below 50 for tropicals, and below 40 for succulents. But there's a bit more to consider when transitioning or acclimating plants.
Because your plants will essentially be moving from one climate to another, this can be a very stressful period for them (read: they're sometimes stressed to an early grave). The light they receive will be radically different inside than it was out. The humidity will be different. The air movement, the temps, the water – the environment that your plants have grown accustomed to throughout the summer is about to get flipped on its head. But by adding a couple of steps to the migration from outdoors to in, you can help your plants to deal with it all well.
1) Replicate the Environment. First, consider the specifics of your indoor environment in relation to the specifics of the environment your plants have enjoyed through the warm season. Now try to replicate that.
If your plants have been getting x hours of filtered sunlight in their outdoor spot, for example, try to replicate that indoors with windows, artificial lighting, or a combination of the two. Do remember that artificial lighting can’t be compared 1-to-1 with the quality of natural lighting, so you’ll probably need to add a few extra hours of lamp light to accomplish a comparable balance, if you don't have an awesome window. Try to replicate the light as well as possible.
If your plants have been thriving in an outdoor setting which has very little air movement and higher humidity, try to replicate that. Be careful to note where your plants are, once indoors, in relation to furnace vents or registers since these may dry them out pretty quickly. If the humidity in your home remains very low, consider adding a small humidifier for the winter, or a humidity tray.
If your plants have been thriving outdoors in a windy setting, consider adding a small fan to your setup or leaving a ceiling fan on once they’re inside.
Making adjustments to your indoor grow-space which mimic the space your plants have just come from can make a world of difference when it comes to seasonal transition and acclimation.
2) Don’t Waste the Daytime. Even though nighttime temps may get too low for your plants, each warm day can be considered a day that your plants would love to be outside. Take advantage of these days and use them to assist with the transition.
When you continue to use the warm daylight hours this way, your plants get taste of your indoor air quality, the lighting that they will need to acclimate to, the air movement, humidity, etc. through the night, but then they have several hours back in their comfort zone (their outdoor spot). In this way, you are slowly acclimating the plant for the months to come.
Replicate the environment. Don't waste the days. I don't believe there is anything better that a plants person can do to assure the success of their over-wintering than to incorporate these two steps into your program.