The simple answer to this is that in the fall and winter drier and cleaner Canadian air is over most of North America and this lets us see the sun's rays better.  But read on...

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The sun emits radiation, some of which we are able to see.  We see the wavelengths that make up the visible spectrum of light.

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When we see sunlight that enters the earth's atmosphere horizontally, the sun's radiation passes through more of the earth's atmosphere than it does from directly above at noon, for example.

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As the sun sets, the earth's atmosphere progressively scatters away violet, blue, green, orange, and yellow light, leaving the brilliant reds that make up the vibrant sunsets we we enjoy so much.