Dew point.

 | Byte | Description                                                        | 
 | :----: | -----------                                                        | 
 | 0    | Index.                                                             | 
 | 1    | Zone for which event applies to (0-255). 255 is all zones.         | 
 | 2    | Sub-zone for which event applies to (0-255). 255 is all sub-zones. | 
