Indoor radon concentrations are subject to diurnal and seasonal variations. In order to obtain an unbiased estimate of the annual mean radon concentration, measurements made over periods less than 12 months have to be adjusted accordingly. In this paper, hourly radon measurements from one uninhabited rural house in Telecí in the Czech Republic have been analysed. The data were collected over a period of 1 y. The behaviour of the radon concentration with time and its relationship with the outdoor temperature, wind speed and atmospheric pressure have been studied. Different estimates of the annual mean radon concentration based on short-term continuous measurements have been assessed.