Incorrect report

The other day the site reported snow in Boston, which was actually falling as I saw in other services and webcams (see screenshot below)

But the report I was getting from http://api.wunderground.com didn't report any snow:

<observation_time>Last Updated on December 8, 10:54 AM EST</observation_time>

<observation_time_rfc822>Mon, 08 Dec 2014 10:54:00 -0500</observation_time_rfc822>

<observation_epoch>1418054040</observation_epoch>

<local_time_rfc822>Mon, 08 Dec 2014 11:19:48 -0500</local_time_rfc822>

<local_epoch>1418055588</local_epoch>

<local_tz_short>EST</local_tz_short>

<local_tz_long>America/New_York</local_tz_long>

<local_tz_offset>-0500</local_tz_offset>

<weather>Overcast</weather>

<temperature_string>21 F (-6 C)</temperature_string>

<temp_f>21</temp_f>

<temp_c>-6</temp_c>