| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 31°F | 53°F | 41°F | 2.9" |
| February | 32°F | 56°F | 43°F | 2.7" |
| March | 39°F | 65°F | 51°F | 3.6" |
| April | 49°F | 75°F | 61°F | 3.8" |
| May | 57°F | 81°F | 68°F | 3.6" |
| June | 65°F | 89°F | 77°F | 4.2" |
| July | 69°F | 91°F | 79°F | 3.9" |
| August | 68°F | 90°F | 78°F | 4.0" |
| September | 62°F | 84°F | 72°F | 4.8" |
| October | 50°F | 74°F | 61°F | 3.4" |
| November | 39°F | 64°F | 50°F | 2.9" |
| December | 35°F | 58°F | 45°F | 3.7" |
| Index | Castalia | North Carolina | National |
| Air quality index | 36 | 35 | 42 |
| Pollution index | 2,959,880 | 2,789,538 | 2,726,193 |
| Measurement | Total |
| Days measured | 363 |
| Days with good air quality | 325 |
| Days with moderate air quality | 38 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Lake Royale, NC | 3,228 | 36 | 28.0% |
| Red Oak, NC | 3,446 | 36 | 28.0% |
| Momeyer, NC | 430 | 36 | 28.0% |
| Rocky Mount, NC | 54,330 | 36 | 28.0% |
| Nashville, NC | 5,521 | 36 | 28.0% |
| Castalia, NC | 276 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Olsburg, KS | 276 | 32 | 36.0% |
| Des Arc, MO | 276 | 54 | 8.0% |
| Henderson Point, MS | 276 | 42 | 16.0% |
| Edmore, ND | 276 | 33 | 34.0% |
| Pilger, NE | 276 | 35 | 30.0% |
| Castalia, NC | 276 | 36 | 28.0% |
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