is expected to rise between one and four feet in the next century due to a combination of warming oceans, melting ice, and land subsidence. Temperatures in North Carolina have risen. Over the last 100 years, the average temperature in Chapel Hill has gone up 1.2 °F (0.7 °C) and precipitation in some parts of the state has increased by 5 percent. Around the year 2080, "temperatures are likely to rise above 95°F approximately 20 to 40 days per year in most of the state, compared with about 10 days per year" in 2016. Seasonal conditions Winter In winter, North Carolina is somewhat protected by the Appalachian Mountains to the west. Cold fronts from Canada are typically reduced in intensity by the mountains. However, occasionally cold air can move from the north or northeast, east of the Appalachian Mountains, from Arctic high pressure systems that settle over the Northeastern or New England states. Other polar and Arctic outbreaks can cross the mountains and force temperatures to drop to about in central North Carolina. Still, temperatures below zero degrees Fahrenheit are extremely rare outside of the mountains. The coldest ever recorded temperature in North Carolina was on January 21, 1985, at Mount Mitchell. The winter temperatures on the coast are milder due to the warming influence of the Atlantic Ocean and the Gulf Stream. The average ocean temperature in Southport in January is still higher than the average ocean temperature in Maine during July. Snow is common in the mountains, although many ski resorts use snowmaking equipment to make sure there is always snow on their land. North Carolina's relative humidity is highest in the winter. Spring Tornadoes are most likely in the spring. Major tornado outbreaks affected parts of eastern North Carolina on March 28, 1984, and April 16, 2011. The month of May experiences the greatest rise in temperatures. During the spring, there are warm days and cool nights in the Piedmont. Temperatures are somewhat cooler in the mountains and warmer, particularly at night, near the coast. North Carolina's humidity is lowest in the spring. Summer North Carolina experiences high summer temperatures. Sometimes, cool, dry air from the north will invade North Carolina for brief periods of time, with temperatures quickly rebounding. It remains colder at high elevations, with the average summer temperature in Mount Mitchell lying at . Morning temperatures are on average 20 °F (12 °C) lower