the areas around the coastal belt of an ocean generally shows less variations in its temperature. the reason is the amount of humidty in the air. the presence of water vapours in the air keeps the temperature from variating too much. also the sea breeze blowing keeps the humidity intact and that in turns keeps the temperature steady.since omaha is located farther from the coast,it shows more variation because there is less humidity in the air. where as eureka which is closer to the sea shows less variation because it has more humidity