The variability of precipitation across the state is related to how storm systems generally move eastward across West Virginia. As they approach the mountains, the air currents must ascend, and as the air cools, it rises, condenses, and can produce precipitation. If there is already precipitation falling, this process can cause rain or snow to intensify. The result is higher annual precipitation totals on the windward side of the mountains, while there is a marked decrease in those totals on the leeward side, known as a rain shadow. The table below shows the variation in the monthly rainfall totals across the state.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Charleston | 3.00 | 3.19 | 3.91 | 3.24 | 4.80 | 4.29 | 4.94 | 3.74 | 3.25 | 2.67 | 3.73 | 3.27 | 44.03 |
| Elkins | 3.23 | 3.10 | 3.96 | 3.80 | 5.12 | 4.40 | 5.36 | 3.84 | 3.63 | 2.85 | 3.38 | 3.26 | 45.93 |
| Martinsburg | 2.44 | 2.34 | 3.52 | 3.34 | 4.09 | 3.76 | 3.67 | 3.08 | 3.57 | 3.05 | 3.13 | 2.71 | 38.70 |
| Parkersburg | 2.95 | 2.70 | 3.73 | 3.27 | 4.30 | 4.02 | 4.21 | 3.61 | 3.08 | 2.86 | 3.36 | 3.10 | 41.19 |
| Snowshoe | 5.77 | 4.87 | 5.80 | 4.82 | 5.38 | 4.84 | 4.96 | 4.70 | 4.33 | 3.82 | 5.03 | 5.55 | 59.87 |