The capability to run weather based analytics against past campaigns or historical sales data is actually a feature that we will be launching soon for WeatherAds. 

Our weather Intelligence and campaign weather analytics module will enable advertisers to measure the impact that weather is having on their campaigns, sales data, or any other business KPIs, and then be able to optimize their campaigns accordingly based on these key insights, to increase performance and profitability.

If you are interested in being a beta users of this feature, just send us a quick email with your name, company and contact info and we'll add you to the VIP list. 

Further Reading: Measuring the ROI on weather targeting your campaigns