OK.. I think I found the issue.. At least on my copy of the ajax-dashboard6.php file -- having a wetbulb temperature that is higher than 32 will set $freezing to false, and in turn, not show the snow icon.. On my file, this is around line 316 or so -- and is:
if ((preg_match('|in|i', $uomRain) and strip_units($wetbulb) > 32)
or (preg_match('|[A-Za-z]m|i', $uomRain) and strip_units($wetbulb) > 0)) { //Check to see if snow is possible
$freezing = false;
} else {
$freezing = true;
So, it looks like whatever values you may have set will be ignored in any instance where wetbulb is higher than 32.. When I bump the 32 up, I get my icon..