Great question! Our jackets, along with most outdoor brands, don't have temperature ratings because there are just too many variables to consider. Simply tagging an arbitrary number to a jacket, though it seems to make things simpler, actually does a disservice for the customer!
The biggest variables to consider are:
Activity Level (What are you doing while you're wearing the jacket?)
What else you're wearing (Merino base layer? A cotton t-shirt? A bikini?)
Body type (Everyone has a different body type, comfort, and regulate heat at different levels.)
These are just a few of the factors that may be constantly changing even though our jacket(s) and the actual temperature stay the same. For these reasons we (and most other brands) don't place a temperature rating on clothing. Though we totally understand that it would be nice and convenient to simply know 'this jacket is rated at 20º' !
With that said we recommend layering up or down depending on the condition and activity level you find yourself in. We're happy to chat with you about what jacket we recommend if you give us some more details on where you plan to be, what the environment will be like, and what you plan on doing in your jacket!