Why is england relatively mild and rainy in winter for its latitude? why is central canada, at the same latitude and during the same season, relatively dry and frigid?

This is because of the presence of Gulf stream in north-western Europe.

Explanation:

Currents of ocean has various contributions on climate. The current of equator that is brought by the Gulf stream of Atlantic in Europe affects a lot the climate of this continent.  In northern Europe, the temperature is moderate due to warmth of the current of this stream.

Its presence and warm current causes difference in temperature between the lands of England or London and Canada or Quebec. As the air flowing over this stream carries enormous water, it causes a rainy weather in London and dry weather in Canada.

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