From Cumulus Wiki

As of version 1.8.9 Build 907, Cumulus will look for the existence of the file 'currentconditions.txt' in the Cumulus folder.

If this file is found Cumulus will use it, update the Current Condition on the display of Cumulus and also use the value to update the <#currcond> webtag

The file will be deleted once Cumulus has processed it, and updated its display. The file is also deleted if the 'current conditions' box on the Cumulus display is changed.

This features allows other tools to produce a Current Condition, write it to the file 'currentconditions.txt' and have Cumulus work with it.

Example Format

Wet and Windy.  Low cloud