“Go Metric,” a site by the U.S. Metric Association; there is a lot at this site:
http://www.us-metric.org/#metric-info
Temperature is discussed at this site:
http://www.allmeasures.com/temperature.html
Unit conversions:
https://www.conversion-metric.org/
The following two sites are dictionaries of units of measurement:
This site has many nice links to other sites.
http://www.unc.edu/~rowlett/units/index.html
This site is very complete dictionary.
http://www.ex.ac.uk/cimt/dictunit/dictunit.htm