Degrees Fahrenheit -99 1901-2000 base period 1901-2000 20100 Pacific Northwest Basin 32.4 101 30.1 2.3 20200 California River Basin 47.0 107 44.8 2.2 20300 Great Basin 35.0 110 32.2 2.8 20400 Lower Colorado River Basin 46.1 116 42.8 3.3 20500 Upper Colorado River Basin 26.7 71 25.6 1.1 20600 Rio Grande River Basin 45.0 75 44.2 0.8 20700 Texas Gulf Coast River Basin 49.5 47 50.2 -0.7 20800 Arkansas-White-Red Basin 38.6 40 39.3 -0.7 20900 Lower Mississippi River Basin 46.8 28 48.4 -1.6 21000 Missouri River Basin 24.8 60 24.9 -0.1 21100 Souris-Red-Rainy Basin 10.8 44 12 -1.2 21200 Upper Mississippi River Basin 21.8 27 23.9 -2.1 21300 Great Lakes Basin 21.0 19 23.5 -2.5 21400 Tennessee River Basin 39.2 25 41.4 -2.2 21500 Ohio River Basin 31.6 26 33.8 -2.2 21600 South Atlantic-Gulf Basin 48.2 20 50.3 -2.1 21700 Mid-Atlantic Basin 29.8 32 31.3 -1.5 21800 New England Basin 20.9 47 21.2 -0.3