I Finally Found Out Why The NWS Sometimes Say It's -0 Out

When the National Weather Service says the temperature outdoor is 'minus 0',
believe it or not, it's accuracy, and not a mistake.

Friday was a relatively cold one in Vermont.

At the web site for the National Weather Service office in South Burlington at one point Friday morning, I saw that the temperature in Burlington was listed as -0 degrees. That's right. Zero degrees below zero.  

Huh? I've seen that before on their site and always wondered what the heck was going on.

Maybe the guys and gals at the NWS were just glass half empty kind of people, giving a pessimistic view to a cold morning.

Thankfully, they set me straight with a geeky but great explanation of why it was minus zero outdoors.

The Automated Surface Reporting System, or ASOS, is the nation's primary surface weather observing network and is widely used at weather stations all over the United States, including the official observing site at the Burlington International Airport.

When I saw that minus 0 Friday morning, it was actually -17.8 degrees Celsius.  The ASOS reports temperatures to every tenth of a degree. Instead of rounding the temperature to -18C, it kept it at -17.8 C.  That temperature is -0.04F.  Therefore, the -0 report was there because it was actually a fraction of a degree below zero, but it was closer to 0 than -1, says the National Weather Service.

Now it makes sense, right?  Thank you to the NWS office in South Burlington  for setting us straight!

As temperatures rose from well below zero this morning, I'm sure it was once again minus 0 at some point today.