The simple answer is we don't know.
There are a good number of weather forecasting sites on the internet. But there are not really much help. Lets face it if any one weather forecast site always got it right the rest would go out of business.
To prove this point we have put together a Weather Forecast page. On the Weather Forecast page you will find Weather Forecast for various races during the year. You can create your own forecast page by adding the event to the Weather Forecast Page.