It's not the amount of indirect or direct sunlight that matters, it's the strength of the sunlight, if you live somewhere where the sun's rays are strong enough it's adequate for vitamin D even if it is often cloudy. Most of Canada is more southernmost and thus has stronger sunlight, than the UK. Much of the US is at a similar latitude to Southern Europe and even North Africa. In the UK it's generally considered that only cities north of Birmingham you may have a problem with getting adequate sunlight exposure for enough of the year, anywhere more southerly than this it isn't considered a problem-and even we in the South are far more Northernmost than the vast majority of the North American continent. Vitamin D deficiency is a very complex issue, some are deficient due to genetic factors or illness causing poor absorption but this isn't the case with most people. Also when it comes to rickets vitamin D deficiency/lack of sunlight isn't the only cause, there are others such as having a diet where unleavened flat breads are a daily staple. There is something in wheat that when not combined with yeast, blocks absorption of vitamin D, calcium and other minerals needed for healthy bones xx