The following values are percentages of occurrance in different flying classes. The values are derived from observations taken over a 43 year period between 1948 and 1990. * is a value greater than zero but less than 0.5 percent.
| Total Skycover <= 3/10 & Visibility >= 2½ miles | ||||||||||||||
| Hour | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Ann | #yrs |
| 1 am | 39 | 50 | 53 | 64 | 75 | 86 | 92 | 91 | 87 | 81 | 60 | 41 | 68 | 43 |
| 4 am | 35 | 46 | 51 | 61 | 72 | 83 | 89 | 90 | 86 | 78 | 58 | 38 | 66 | 43 |
| 7 am | 22 | 32 | 37 | 49 | 63 | 78 | 83 | 82 | 76 | 63 | 38 | 21 | 54 | 43 |
| 10 am | 21 | 31 | 35 | 46 | 60 | 77 | 83 | 83 | 79 | 63 | 39 | 21 | 53 | 43 |
| 1 pm | 22 | 28 | 32 | 42 | 58 | 78 | 84 | 81 | 77 | 62 | 38 | 21 | 52 | 43 |
| 4 pm | 24 | 30 | 34 | 42 | 57 | 78 | 82 | 80 | 77 | 63 | 43 | 26 | 53 | 43 |
| 7 pm | 34 | 42 | 46 | 52 | 61 | 77 | 82 | 81 | 81 | 71 | 53 | 36 | 60 | 43 |
| 10 pm | 39 | 47 | 51 | 64 | 74 | 87 | 90 | 91 | 85 | 78 | 56 | 41 | 67 | 43 |
| ALL | 29 | 38 | 42 | 52 | 64 | 80 | 85 | 84 | 81 | 69 | 47 | 30 | 59 | 43 |
| SFC wind speeds 4-10 knots, Temps 33-89oF & no Precipitation | ||||||||||||||
| Hour | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Ann | #yrs |
| 1 am | 52 | 60 | 65 | 62 | 66 | 68 | 65 | 65 | 61 | 63 | 56 | 52 | 61 | 43 |
| 4 am | 49 | 57 | 59 | 64 | 66 | 62 | 53 | 53 | 57 | 55 | 54 | 47 | 56 | 43 |
| 7 am | 49 | 53 | 58 | 65 | 68 | 66 | 65 | 63 | 60 | 56 | 54 | 47 | 59 | 43 |
| 10 am | 49 | 52 | 58 | 66 | 72 | 65 | 50 | 60 | 62 | 60 | 54 | 51 | 58 | 43 |
| 1 pm | 60 | 62 | 68 | 69 | 59 | 43 | 15 | 23 | 47 | 69 | 65 | 61 | 53 | 43 |
| 4 pm | 65 | 64 | 69 | 60 | 43 | 25 | 06 | 13 | 36 | 69 | 73 | 63 | 49 | 43 |
| 7 pm | 60 | 64 | 71 | 74 | 69 | 51 | 28 | 53 | 65 | 67 | 67 | 61 | 61 | 43 |
| 10 pm | 57 | 63 | 67 | 68 | 69 | 71 | 68 | 68 | 68 | 66 | 63 | 58 | 65 | 43 |
| ALL | 55 | 59 | 64 | 66 | 64 | 56 | 43 | 49 | 57 | 63 | 61 | 55 | 58 | 43 |
| Ceiling >= 1000 feet, visibility >= 2½ miles & wind <= 10 knots | ||||||||||||||
| Hour | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Ann | #yrs |
| 1 am | 75 | 86 | 94 | 93 | 91 | 91 | 99 | 98 | 98 | 97 | 90 | 72 | 90 | 43 |
| 4 am | 69 | 83 | 95 | 95 | 96 | 97 | 99 | 99 | 99 | 98 | 87 | 68 | 91 | 43 |
| 7 am | 59 | 78 | 91 | 93 | 94 | 96 | 99 | 99 | 98 | 95 | 77 | 57 | 86 | 43 |
| 10 am | 59 | 79 | 88 | 92 | 93 | 93 | 96 | 97 | 96 | 95 | 80 | 57 | 85 | 43 |
| 1 pm | 69 | 82 | 86 | 85 | 80 | 79 | 73 | 77 | 88 | 94 | 84 | 67 | 80 | 43 |
| 4 pm | 75 | 83 | 80 | 70 | 61 | 59 | 53 | 61 | 73 | 88 | 86 | 71 | 71 | 43 |
| 7 pm | 82 | 91 | 91 | 86 | 79 | 80 | 90 | 94 | 95 | 95 | 93 | 80 | 88 | 43 |
| 10 pm | 80 | 90 | 91 | 87 | 82 | 84 | 90 | 93 | 94 | 97 | 90 | 79 | 88 | 43 |
| ALL | 71 | 84 | 89 | 87 | 84 | 85 | 87 | 89 | 92 | 95 | 85 | 68 | 85 | 43 |