Average solar radiation (watts/sq.m.) for selected cities jul aug sep oct nov dec jan feb mar apr may jun Atlanta, GA 257 246 201 166 30 102 106 140 184 236 258 271 Barrow, AK 208 123 56 20 0 0 0 18 87 184 248 256 Bismark, ND 296 251 185 132 78 60 76 121 170 217 267 284 Boise, ID 324 275 221 152 88 60 69 113 164 235 284 309 Boston, MA 240 206 165 115 70 58 67 96 142 176 228 242 Caribou, ME 246 218 161 102 53 51 66 111 178 194 229 232 Cleveland, OH 267 239 182 127 68 56 60 87 151 182 253 271 Dodge City, KS 311 287 239 184 138 113 123 153 202 256 275 315 El Paso, TX 324 309 278 224 178 151 160 209 266 317 346 353 Fresno, CA 323 293 243 182 117 77 90 143 212 264 308 337 Greensboro, NC 263 235 197 156 118 95 97 134 171 227 257 273 Honolulu, HI 305 293 271 245 208 176 175 200 234 262 300 297 Little Rock, AR 270 250 214 167 118 91 96 127 173 220 256 272 Miami, FL 260 246 216 188 171 154 166 201 238 263 267 257 New York, NY 251 238 175 127 77 62 71 102 151 183 220 255 Omaha, NE 275 252 192 142 96 80 99 134 172 224 248 272 Rapid City, SD 288 262 208 152 99 76 90 135 193 235 259 287 Seattle, WA 242 209 150 84 44 29 34 60 118 174 216 228 Tucson, AZ 304 286 281 216 172 144 151 195 264 322 358 343 Washington, DC 267 190 196 145 75 64 101 124 153 182 215 247 Are sunny summer places also sunny winter places? Check correlation of sampled U.S. solar radiation (july with other months) month d st. dev. probd spearman-r probrs jul 0.00 -4.358899 0.000013 1.000000 0.000000 aug 122.00 -3.958458 0.000075 0.908133 0.000000 sep 218.00 -3.643896 0.000269 0.835967 0.000004 oct 384.00 -3.098495 0.001945 0.710843 0.000443 nov 390.50 -3.077642 0.002086 0.706060 0.000503 dec 622.00 -2.318075 0.020445 0.531803 0.015806 jan 644.50 -2.244251 0.024816 0.514866 0.020181 feb 483.50 -2.772503 0.005563 0.636056 0.002573 mar 497.00 -2.728208 0.006368 0.625894 0.003158 apr 405.50 -3.027925 0.002462 0.694654 0.000677 may 264.00 -3.492371 0.000479 0.801205 0.000022 jun 121.50 -3.960099 0.000075 0.908509 0.000000