There has been one data source that I’ve been looking for, for at least a couple months now: Historical Weather Data. I would’ve thought that this data would be out in the open and readily available, but I have been unable to locate any reliable source which provides this. It wasn’t until last week, when I was traversing Weather Underground (my weather web site of choice), that I began to notice some features that let you get closer to historical data, which really excites me. Unfortunately, there are some limitations on retreiving the data, the most important of which is that you cannot retreive more then 1 year’s worth of data at a time and only for one location (e.g. an airport). Additionally, the availability of the data tends to vary. Data entries from the pre-dot-com era are missing some finer measurements, but shouldn’t effect most people.
Historical Weather Data for Rochester, NY from 07/03/2000 to 07/03/2001
If you don’t feel like writing your own data aggregator to run over their data, I recommend that you look at their Trip Planner, a very handy tool for determining what the weather, at a specific location, is most likely to entail.