The biggest problem are the roots, which will suffer near those temperatures. Putting the pots on the ground, covered with mulch helps (Or, if it snows, a nice snow blanket will raise the temperature to near freezing). If you do this in a garage / shed you win another few degrees. If you still do get temps that far down in the rootzone, a frost-protection cable burried in sand on top of which you place the pot could help. Add a time for the coldest hours of the night? And/or build a coldframe for your trees, which is what I hear many people in true cold climates do.

it says it's going to hit -12 C. is that still fine or no?

im leaving them in my covered car port. does that help at all?

bonsainoobnoob wrote:

it says it's going to hit -12 C. is that still fine or no?

im leaving them in my covered car port. does that help at all?

That should not be a problem.

Have you seen my post on frost damage?
www.growingbonsai.net/what-kills-bonsai-in-winter/