DD2 was a June heatwave baby, compared to DD1, who was an end of November, snow on the ground one.
Newborns can still be cold when not actually against your body, such as in a sling, so it was very similar, other than no snowsuit when outside in the first couple of weeks.
I found it easier after that because there was less in the way of a difference between indoors and outside clothes.
The main one was putting her into cotton shortsleeved vest and babygros instead of the terry fabric ones with a longsleeved vest and not always putting a cardigan on her, keeping it with the cellular blanket at her feet in the pram, so more like how DD1 would have been dressed indoors in winter with the heating on.
By August, I was switching to footless babygros or leggings/vest/light top/cardigan and tiny cotton socks ❤and by the end of September, I was adding fleecy trackie bottoms or she'd wear vest/tights/dress/cardigan and hat under a blanket. That winter was very wet though, so she spent a lot of time when out in her little greenhouse/under the raincover 😁, which kept her warmer.
You'll notice how much easier it is to get a shortsleeved vest on and how nice the lighter fabric babygros are - it's so much quicker to get them ready for the school run when you're in a hurry in summer, as you can pretty much pick up baby, put into pram, chuck a blanket in there in case of it feeling a bit cooler and you're out the door instead of getting them into a snowsuit, adding a hat, then coming back and trying to get them out of the snowsuit without waking up.