Critical frequency and maximum electron density of F2 region over four stations in the North American sector

► The performance of IRI to predict foF2 for low solar activity years is checked. ► Data were obtained from the University of Massachusetts Lowell DIDBase. ► In general, good predictions are obtained for middle latitude stations. ► The worst predictions are given for high latitude station. Cases where the error model in predicting NmF2 reaches high values are observed.