[en] Observations of environmental radon are to be important for humankind from a medical point of view. We have analyzed atmospheric radon concentration taken from our data set of 2000-2004 in relation with a meteorological point of view. Radon concentration attains usually maximum value, 15 Bq/m³ or so, in the morning after sunrise in fine days. It decreases gradually in the afternoon and attains minimum concentration after 2-3 hours from the time of the maximum temperature. Seasonal variations of radon concentration commonly occur in early summer as low value and in early winter as high value in Toyama. And also, the concentrations of radon tend to decrease in rainy high humidity days. Wind speed and wind direction also have some relations with a change of the concentrations. Generally, the concentrations decrease in high wind speed and increase in SSW to WSW wind directions. (author)