At 7 weeks of age, they should be fully off any heat, so they are fine.
I've got broody hatched babes that go out with momma in the snow at day 3 or 4, using her as a warming hutch in between excursions in their down coats. They would die without momma's body heat to warm them when they felt chilled.
However, by 4 to 5 weeks of age, chicks have fully feathered, so they are in the elements at all temps with shelter from direct storms.
The only reason to slow the progression is if you have artificially brooded with heat lamps. Then you do have to harden them to the cold.
You've got a covered run, so they'll be fine at that ambient temp....as long as they are off heat lamps.
LofMc