> so any Arctic air brought down in the US won't "feel" as cold compared to if it happened in January because we are in a warmer part of the year.

I read this pretty simply as "March is warmer than January". More hours of daylight, more direct angle, etc. Anyone living closer to the tropics knows that feeling of "it's cold but the sun is out" compared to being further away in winter.

Yeah, that makes sense. I was tripped up a bit because "march is warmer" sounds to me like an effect, not a cause - and it becomes paradoxical if there is a massive cold front underway at the same time.

But if they mean, there are other seasonal factors - such as daylight - that counteract the cold spell, which aren't there in winter, it makes more sense.

Imaging increased warming from sunlight raising ground and building temperatures probably impacts “felt” temperature quite a bit.

There a few different heat transfer mechanisms, with conduction and radiation being the big ones we care about here. Cold air impacts heat transfer via conduction, but temperature of surrounding surfaces (like buildings and the ground) impacts radiative heat transfer, which makes us a significant portion of your bodies heat transfer into it’s surrounding environment. Which is the reason why a clear night is colder than an overcast night. The clouds above reflect a significant amount of radiant energy back at you on a cloudy day, and on a clear night you’re directly exposed to cold emptiness of space which will radiate effectively zero heat back at you.

Good place to experience the difference between conduction and radiative heat, is being near a camp fire on a cold night. The camp fire doesn’t really warm the air around your body, but the emitted IR has a huge impact. Hence you end up with a very warm front, while still having a very cold back.