I used a smartapp for years that worked perfectly for this purpose but with the old groovy apps going away I had to come up with a different way of doing this. You have to create 40 routines but that took me about an hour with the copy function in routines. Basically, one routine for Humidifier on and one for off for each temperature range. This prevents raising the humidity in your house too much and frost and ice forming on your windows and water damage and mold inside your walls. Originaly I didnt want to do this because of the 200 routine limit, then they raised it to 1000 so I went this route.

Create the routines and then just keep using the copy function and changing the values each time.

- If outside temp is 38.6F or higher (precondition) and inside humidity is 44% or lower then turn on Humidifier.

2, If outside temp is 38.6F or higher (precondition) and inside humidity is 50% or higher then turn off Humidifier.

3. If outside temp is between 36.6F and 38.5F (precondition) and inside humidity is 43% or lower then turn on Humidifier.

4. If outside temp is between 36.6F and 38.5F (precondition) and inside humidity is 44% or higher then turn off Humidifier.

Keep going untill you get all the way down to the lowest temprature you will see in your area. My outside strips thermomter only goes down to -4 F so thats where I stopped. After I figure out a new way to create a weather tile then I may create more routines based on the current temprature in my area.

It gets cold here sometimes in North East PA, I have seen - 36 F here a few years. Below you will find the logic for all the routines. I have tested this against the original smartapp and it works perfectly. Let me know if you have any questions.

DS = deck strips thermometer (outside Temp ) DA â€“ Dining room Aeotec (inside Temp) DH= Dining room Humidifier (smart plug)

- If DS = 38.6F or higher and DA = 44% or lower then turn on DH.
- If DS = 38.6F or higher and DA = 50% or higher then turn off DH
- If DS = 36.6F and 38.5 and DA = 43% or lower then turn on DH.
- If DS = 36.6F and 38.5 and DA = 44% or higher then turn off DH
- If DS = 34.6F and 36.5 and DA = 42% or lower then turn on DH.
- If DS = 34.6F and 36.5 and DA = 43% or higher then turn off DH
- If DS = 32.6F and 34.5 and DA = 41% or lower then turn on DH.
- If DS = 32.6F and 34.5 and DA = 42% or higher then turn off DH
- If DS = 30.6F and 32.5 and DA = 40% or lower then turn on DH.
- If DS = 30.6F and 32.5 and DA = 41% or higher then turn off DH
- If DS = 28.6F and 30.5 and DA = 39% or lower then turn on DH.
- If DS = 28.6F and 30.5 and DA = 40% or higher then turn off DH
- If DS = 26.6F and 28.5 and DA = 38% or lower then turn on DH.
- If DS = 26.6F and 28.5 and DA = 39% or higher then turn off DH
- If DS = 24.6F and 26.5 and DA = 37% or lower then turn on DH.
- If DS = 24.6F and 26.5 and DA = 38% or higher then turn off DH
- If DS = 22.6F and 24.5 and DA = 36% or lower then turn on DH.
- If DS = 22.6F and 24.5 and DA = 37% or higher then turn off DH
- If DS = 20.6F and 22.5 and DA = 35% or lower then turn on DH.
- If DS = 20.6F and 22.5 and DA = 36% or higher then turn off DH
- If DS = 18.6F and 20.5 and DA = 34% or lower then turn on DH.
- If DS = 18.6F and 20.5 and DA = 35% or higher then turn off DH
- If DS = 16.6F and 18.5 and DA = 33% or lower then turn on DH.
- If DS = 16.6F and 18.5 and DA = 34% or higher then turn off DH
- If DS = 14.6F and 16.5 and DA = 32% or lower then turn on DH.
- If DS = 14.6F and 16.5 and DA = 33% or higher then turn off DH
- If DS = 12.6F and 14.5 and DA = 31% or lower then turn on DH.
- If DS = 12.6F and 14.5 and DA = 32% or higher then turn off DH
- If DS = 10.6F and 12.5 and DA = 30% or lower then turn on DH.
- If DS = 10.6F and 12.5 and DA = 31% or higher then turn off DH
- If DS = 8.6F and 10.5 and DA = 29% or lower then turn on DH.
- If DS = 8.6F and 10.5 and DA = 30% or higher then turn off DH
- If DS = 6.6F and 8.5 and DA = 28% or lower then turn on DH.
- If DS = 6.6F and 8.5 and DA = 29% or higher then turn off DH
- If DS = 4.6F and 6.5 and DA = 27% or lower then turn on DH.
- If DS = 4.6F and 6.5 and DA = 28% or higher then turn off DH
- If DS = 2.6F and 4.5 and DA = 26% or lower then turn on DH.
- If DS = 2.6F and 4.5 and DA = 27% or higher then turn off DH
- If DS = 0.6F and 2.5 and DA = 25% or lower then turn on DH.
- If DS = 0.6F and 2.5 and DA = 26% or higher then turn off DH

Update, these routines ran fine when they were running in the cloud. After I finished my migration to Edge and the same routines were running locally on the hub, they would only work once in a while. Sometimes they would work for a half a day or so and then stop. I have moved away from this and started using Sharptools and moved all my migrations over there. The Smartthings routines are just to buggy and disappear and change by themselves. Smartthings told us we could migrate all of our Webcore pistons and smartapps to routines, which you can but then they donâ€™t run reliably.