Right, here we go....

This is beteljuice's table, but corrected by me. What I did was edit all of the values in the first record of EasyWeather.dat, changing the numbers to increment by 1 from 20 to 48 - but using similar data to the original.

I then ran EW, clicked on history, found the first record in the file all neatly numbered up (but not necessarily in sequential order) and with a corresponding label. That enabled me to tie each data field to an actual label.

As near as I can tell at the moment, the data in the .dat file is always stored in the same basic format and then any conversion is done within the software (to change from for instance deg C to deg F etc..)

1/ Record No.
2/ date / timestamp (ISO format) of when Software interogated wx
3/ date / timestamp (ISO format) of RECORD
4/ recording interval (minutes)
5/ indoor humidity
6/ indoor temp. C
7/ outdoor humidity
8/ outdoor temp. C
9/ Dew Point C
10/ Windchill C
11/ baro - absolute hPa
12/ baro - relative hPa
13/ windspeed - metres per sec
14/ wind level - beaufort
15/ windspeed GUST - metres per sec
16/ ? windspeed GUST -beaufort
17/ wind direction: 0 - 15 options 8 = S(outh) ???????
18/ wind direction: NNW - probably language dependent
19/ ? eg. 0 - integer
20/ ? eg. 0.0 - 1 dec place
21/ ? eg. 0.0 - 1 dec place
22/ 24 hour rain - mm
23/ Week's rain - mm
24/ Month's rain mm
25/ Total of rainfall mm
26/ Doesn't show up in history table????
27 => 34/ ? eg. 0 - integer

I think the above is correct, but no guarantees.