Yes, there is an easy way to add those tags.
With the distribution WCT-plugin.zip came two files:
WeatherCat-webtags.txt
gen-WCTtags.php
You can add tags to the WeatherCat-webtags.txt using an ASCII text editor and this format with one tag per line:
wvar<tab><WeatherCat tag><tab><optional comment>
<tab> is the Tab character which is used as a field delimiter in the Weather-Cat-webtags.txt file.
You can add something like wvar STAT$WINDCHILL:MIN:ALLTIME$ Lowest wind chill alltime
wvar STAT$WINDCHILL:MIN:ALLTIME:TIME$ Time of lowest wind chill alltime
and repeat for the other variables you'd like to add.
Save and upload the WeatherCat-webtags.txt to your website.
Then view gen-WCTtags.php?comments=y on your website to generate a WCTtags template file. Save the file over your current WCTtags template.
Then you can refer to the values as
$WX['STAT:WINDCHILL:MIN:ALLTIME'] and
$WX['STAT:WINDCHILL:MIN:ALLTIME:TIME']
in your PHP code.
Hope this helps...
Best regards,
Ken