Recently we were asked what are the “zones” that the National Weather Service uses and what is their purpose. This is a very good question.

The National Weather Service in Boulder breaks down Colorado (and other states) into various zones for use when issuing forecasts, watches, warnings, etc. If you look at the text of these, you will see something like this:

SHORT TERM FORECAST
NATIONAL WEATHER SERVICE DENVER CO
1125 AM MDT MON JUL 07 2008

COZ040-041-043-045-071930-

Notice the part in bold. That tells you which zones are affected by the warning – in this case, the CO of course means Colorado.  The “Z” part tells you zones 40, 41, 43 and 45 are affected. So what zone do you live in? In general, if you are in the Denver metro area, you are in either zone 39 or zone 40. You can click here for a PDF map of all Colorado zones.