If you want to find what the weather was like for your ancestor's wedding day, there is a daily weather summary for the Sussex coast (well to be precise, Windover Hill) for most days from 10th Feb 1811 to 12th Dec 1812, in William Vine's diary "Wheathers".
You can find a full set of page images of this diary online at www.williamvine.net. There are a few pages missing (5th May - 15th June 1811), and some others are illegible.