La Crosse weather stations
The software used with the device is Heavy Weather, and while it peforms its role of reading, displaying, and storing data from the weather station, Heavy Weather Software is quite limiting and inflexible. Of course, if you are reading this you have probably already switched to Cumulus and found its advantages.
Using the Heavy Weather program, you can open the History window and save the weather data from the desired history file as a text file ready to import any pre-Cumulus observations. See Monthly_log_files or EasyWeather_Format for more inspirational tips on such imports. During normal running, HeavyWeather software outputs to a file called history.dat, but each of these holds only a limited number of records. La Crosse also offer Pro Weather Station Software to analyse the output of Heavy Weather.