[swsieber]

It is a wash, but judging from the comments the heavy rains/gloom come in the winter... so it could be a real explaination.

[acchow]

Actually, just the opposite. If most of the cloud cover/gloomy weather happened in the winter, then much of the clouds would be at night...which wouldn't dramatically reduce your sunshine hours.

If the gloominess happened during long days, you'd really see a drop in mean sunshine hours.