German reporting in. According to Weatherspark [1] starting November to March around 70% of the days are cloudy and it's cold so you would barely expose 15% of your body to the remaining sun. In feburary, around midday, on a cloudy day you don't make enough vitamin d. And even on a cloudless day it takes more than 4 hours around midday to get the daily recommended dose. [2]. Being a dog owner I spend a lot of time outside, also during midday and 3/4 of the year I go for a run around midday every other day. Last year in january I was diagnosed with severe vitamin D deficiency at around 6ng/ml. Took a few months to get that back to normal using supplements.

[1] https://weatherspark.com/y/68301/Average-Weather-in-Hamburg-... [2] https://fastrt.nilu.no/VitD_quartMEDandMED_v2.html