nantucket average temperature september
n/a. The highest average temperature in Nantucket is August at 70.9 degrees. The coldest average temperature in Nantucket is January at 29.7 degrees. The most monthly precipitation in Nantucket occurs in January with 0 inches.The Nantucket weather information is based on the average of the previous 3-7 years of data.he Nantucket, MA air quality index is a median value which considers the most hazardous air pollutants. The Nantucket, MA air quality index is 18.4% less than the Massachusetts average and 33.6% less than the national average.