Higher PG for Wicking
One of the things that's the most obvious is that it makes your eliquids a bit more viscous. When your eliquids are too thick, it brings up a few issues. One of them being wicking. Wicking is vital in making sure you do not get that dreaded "dry hit". The cold makes the VG slow down, and more molasses-like. When your VG becomes too viscous, it doesn't soak into your wicks as nicely. And we all know what happens when your wicks aren't juiced up. Another issue that arises concurrently, is airflow. Because when you're dripping this viscous VG on your coils, and it's not soaking into the coils correctly, this can easily block airflow. And again, as we all know airflow is vital to the development of flavor. So one of the easiest ways to rid of this problem is to just make high PG eliquids. I generally keep my eliquids at 70VG/30PG, so 60/40 will alleviate most of that issue. Though, when it's really cold, sometimes I'd need to go down to 50/50. One of the misconceptions about doing this is that you need to change the recipe. Whether it's increasing percentages or decreasing them, I have found that keeping the concentrations the same brings up no ill effects. So just drop your PG, keep everything else the same, and you shouldn't have issues with wicking or airflow clogging during the cold.
Another issue that arises from cold weather is a bit more subdued. What I'm talking about is sickness, or runny noses. Most of the flavor that we get comes from our noses and our sense of smell. When you're sick, your sense of smell is hindered, and it's the reason you can't taste much of anything. When it's cold out, the same sort of issues arise even when you're not sick. A runny nose will make it so it's a bit more difficult to get the full flavor and nuance from your recipes. This is a bit more difficult to prevent if you're someone who must always be in cold weather. The only prevention I have found is to just avoid cold weather. Also, if you're testing recipes, it's best to do them all after your body has come to room temp and your nose back to normal. You won't get the full flavor of your recipes if you're trying to test them out in the cold with your nose running. Just wait until you can get somewhere warm and cozy to do your note taking and flavor testing. This might seem like common sense to some, but others live in cold environments and might wonder why they can't taste the small subtle flavors others might be getting.