The highest average temperature in Blackshear is August at 81.3 degrees. The coldest average temperature in Blackshear is January at 52.9 degrees. The most monthly precipitation in Blackshear occurs in January with 0 inches.oading... The Blackshear, GA air quality index is a median value which considers the most hazardous air pollutants. The Blackshear, GA air quality index is 21.1% less than the Georgia average and 35.6% less than the national average.