Precipitation is one of the most studied atmospheric parameters, and its occurrence has a direct relationship with the atmospheric circulation pattern. This study investigates the relationship between relative vorticity in the mid‐troposphere (at 500 hPa), and precipitation amounts and the number of rain days over the period 1979–2013 in Iran. Relative vorticity was calculated using the u and v components of the wind data from the European Centre for Medium‐Range Weather Forecasts (ECMWF) interim reanalysis (ERA‐Interim) over Iran, with 0.125° spatial resolution. Gridded daily precipitation data from the Asfazari National Dataset with a spatial resolution of 15 × 15 km, covering the same period, were also used. Pearson's correlation coefficient was used to investigate, at the 90% confidence level, the relationship between relative vorticity, and monthly precipitation amount and number of rain days. The significance of the trend for relative vorticity for different months, at the 90% confidence level, was evaluated using the nonparametric modified Mann–Kendall test. The results showed a significant relationship between relative vorticity and the number of rain days and precipitation amounts over Iran. In temporal terms, the correlations between relative vorticity and the number of rain days and precipitation amounts are strongest during the months of high precipitation over Iran, especially in November and December. In spatial terms, eastern Iran exhibits the strongest relationship between precipitation and relative vorticity at the 500 hPa level. Examination of the time series data showed that the monthly precipitation amounts and numbers of rain days fluctuate in line with changes in relative vorticity during the period of study. Analysis of trends in the relative vorticity data also showed, at the 90% confidence level, that the maximum variations in relative vorticity occurred in autumn and winter, respectively. Trend analysis also showed a decreasing trend in relative vorticity in March and an increasing trend in November.