The paper examines seasonal variability in the spatial distribution and magnitude of horizontal gradients of temperature, salinity and density in large-scale surface frontal zones in the North Atlantic Ocean. Monthly average temperature and salinity data at the 0.5 m horizon from the ORAS5 oceanic reanalysis (1958-2021) are used. High gradients of temperature exceeding 2°C/100 km, those of salinity exceeding 1 PSU/100 km, and those of density exceeding 1 kg·m⁻³/100 km were observed in the subpolar and temperate regions in fronts along large-scale currents carrying warm salty waters from the southern latitudes (Gulf Stream, North Atlantic Current) and cold waters with low salinity from the Arctic regions (Labrador Current, East Greenland Current). These fronts occur throughout the year. High salinity and density gradients are also observed in the tropical summer in the front at the edge of the Amazon River plume, resulting from seasonal river flow. In these five frontal zones, areas were identified for which quantitative estimates of seasonal variability of gradients are provided. In the subpolar and temperate latitudes, maximum temperature gradients are observed in winter. Warming up of water in the summer season is accompanied by a decrease in gradients. The greatest range of seasonal variability of temperature gradients was noted in the frontal zones of the Gulf Stream and the East Greenland Current. In summer, in the fronts of subpolar regions, salinity gradients increase due to the melting of Arctic and continental ice and an increase in the influx of waters with low salinity. In the frontal zone of the East Greenland Current, as well as at the boundary of the Amazon River plume, the highest range of seasonal changes in salinity and density gradients was noted. In these areas, the contribution of salinity to seasonal changes in density at the ocean surface increases.