Do not begin your novel by describing the weather. I don't know why so many of you seem to think that grandiose descriptions of seasonal environmental effects (new grass, falling leaves, snow, rain, etc.) make a compelling first line.
In case you haven't heard, the weather is boring. Although you may later have the opportunity to share your uniquely special wonderment at the beauty of nature, please save it for your saggy middle - I'm sure it needs some shoring up anyhow.
The first line of your novel should draw us into the story. It should set the tone, give us an idea of what's to come. Is your book about the weather? I didn't think so. When you start with something bland and irrelevant, the reader draws certain conclusions.
A Sad, Sad Reader of Unpublished Fiction.