The current weather conditions are based on a private weather station on the edge of the park. Full historic weather details and forecasts based on this local data can be found on the following site…
The following two sites also show the data publicly, but use imperial measurements for the public view, which you can only change by signing up for a free account.
Weather Underground also supplies the data to AccuWeather, who use it to localise their forecast.
Acknowledgement: Colin Robbins