Access attribute of "from state"

Is there a way to access an attribute of the “from state” in an automation triggered by a state trigger?

I want to create a template condition that checks the current temperature attribute of my climate entity, but haven’t had any success with any of my iterations thus far.

I only want this automation to fire if the furnace has been on for 15 minutes and the temperature has not changed.

{{ state_attr(trigger.entity_id, 'current_temperature') <= state_attr(trigger.from_state, 'current_temperature')  }}

I also tried this to no avail (and quite a few other things methinks).

{{ state_attr('climate.downstairs', 'current_temperature') <= trigger.from_state.attributes.current_temperature  }}

from_state is a state object, you can access everything by accessing the properties directly from the object.