with August being the warmest month, though September is usually as warm or warmer than July. Temperatures, humidity, and sunshine Although temperatures as warm as have been recorded on Pico, neither Ponta Delgada nor Angra do Heroísmo, the two largest cities, have ever been warmer than . There has never been a frost, snowfall, freeze or even temperatures below recorded at sea level on any of the islands. The coldest weather in winter usually comes from northwesterly air masses originating from Labrador in Canada. However, since those air masses are warmed up as they pass across the warmer Atlantic Ocean, temperatures by day even then exceed . The average relative humidity can range from 80% at the coast to over 90% above . However, higher elevations above the planetary boundary layer can experience extremely low values close to 10%. Summers are especially humid in August and may increase the perceived temperature by a few degrees. Winters are not only very mild but also very humid and contribute substantially to the annual precipitation. Insolation is relatively low, with 35-40% of the total possible value for sunshine, and higher in topographically lower islands such as Graciosa or Santa Maria, inversely proportional to precipitation. This is directly caused by the orographic lift of humid air masses and is especially pronounced in islands marked by high orography. Hurricanes With a greater rarity, especially in late summer and autumn, despite the northern position that the archipelago occupies, the Azores can be affected by the passage of tropical cyclones, or tropical storms derived from them, some can result from anomalies of low latitude systems while others result from the return, back to the Atlantic, after a route close to or even over the American continent. Though often small and in the process of dissipation, these cyclones result in many of the worst storms the archipelago is subject to. A total of 14 tropical or subtropical cyclones have affected the region in history. Most of them were either extratropical or tropical storms when they affected the region, although several Category 1 hurricanes have reached the Azores. The following storms have impacted the region while at Category 1 strength: Hurricane Fran in 1973 Hurricane Emmy in 1976 Hurricane Gordon in 2006 Hurricane Gordon in 2012 Hurricane Alex in 2016 Several tropical storms have hit the region, including Tropical Storm Irma in 1978 Hurricane Bonnie in 1992 Hurricane Charley