howmuchsun

Vitamin D from sunlight in Portugal

How long you need in the sun to make vitamin D, and when the sun is too low to make any at all, for 3 cities in Portugal.

CityLatitudeElevationVitamin D winter
Lisbon 38.73°N 68 m 11 Nov – 6 Feb (88 days)
Porto 41.15°N 91 m 2 Nov – 16 Feb (107 days)
Braga 41.55°N 190 m 31 Oct – 17 Feb (110 days)

How these dates are calculated