A short overview of the concepts needed to teach weather and climate to elementary and middle school students is provided here:

/files/200201_200300/200248/weather-primer.pdf

Originally published in 1997, this NASA resource still is one of the very best collections of weather and climate activiities for upper elementary and middle school students. It includes a primer on weather and climate science, hands-on activities, and three lessons teaching using different levels of inquiry

Meteorology:  An Educator's Resource for Inquiry-Based Learning for Grades 5-9, by J. Exline, A. Levine, and J. Levine (1997)

The complete resource can be found here: http://www.nasa.gov/centers/langley/science/met-guide.html

Here are some other good hands-on activities that can be used to teach basic concepts related to weather and cliimate:

Here is a link to hands-on activities exploring aspects of weather and climate.  These were developed at the University Corporation for Atmospheric Research (UCAR), in Boulder, CO.  

Kids' Crossing in the Classroom can be downloaded here http://www.trunity.net/files/200201_200300/200220/kids-crossing-ucar.pdf