Indeed. Look for the "UV index" in your local weather reports. If it's below 3 [on a sunny day, during wintertime] it means that the low angle of the sun, even

Indeed. Look for the "UV index" in your local weather reports. If it's below 3 [on a sunny day, during wintertime] it means that the low angle of the sun, even at noon, reduces UV intensity to such an extent that your skin cannot produce vitamin D.