A STEM education program entitled "Come rain or shine" implemented in a primary rural school in southern Greece as part of the "Diffusion of STEM (DI-STEM)" project and the results of its implementation are presented in this paper. The educational program deepened in weather education and intended to develop eight scientific practices for primary students proposed by the NGSS. Students' pretest and posttest questionnaires revealed difficulties in adopting meteorological vocabulary and relative scientific practices through weather measurements in their local environment. Students' answers indicate a variety in their conceptual progress depending on the scientific practice being investigated. They showed great progress in "analyzing & interpreting data, and using mathematics," moderate progress in "developing & using models, and evaluating & communicating data)," limited progress in "asking questions & defining problems," and "planning & carrying out investigations" and a slight setback in "constructing explanations and engaging in argument from evidence." Possible explanations and relative teaching implications for successful STEM education in primary education are discussed.