With the redesigned website the option to switch to metric has disappeared. I have read the previous answers from Mike regarding the selection of that option in the "current conditions" page, but it was removed. You have a good web site, but I believe many people would appreciate having the world's standard units available.
Posted November 11, 2007
MIKE MOSS SAYS: Zdenek, Perhaps there was a transient glitch with the site when you last attempted to access the metric option, but I am unable to duplicate the issue. There is still a "Use Metric Units" link on the "Current Conditions" page that seems to work correctly when I use it. Clicking the link will cause the site to default to metric units for text-based observations and forecasts (it does not affect the forecasts that are generated graphically, such as the 5-day image) until it is switched back by clicking "Use English Units" in the same location.