My sister has always had this issue when she’s cold, since she was a kid. She has no health issues. She’s just a tiny thing that gets cold really easily and the lower half of her nail beds turn bluish. Not her fingertips though.
Mine will do this when it’s really cold and windy out, but not as bad as my sister’s.
Very cold temperatures can temporarily slow the flow of blood through the skin leading to the bluish color, but this usually goes away when the temperature becomes warm. Blue nails may occur as a side effect of a medication. Blue nails are also caused by problems that reduce the amount of oxygen in the blood, such as asthma and COPD, severe anemia, cold exposure, exposure to high altitude, peripheral arterial disease, or shock.
The cold will turn your nail bed blue. It’s normal in the sense that you are cold and it is a normal reaction. It isn’t good though. You don’t want to be like that for very long periods.