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 | 27 | 47 | 57 | 66 | 76 | 87 | 89 | 89 | 85 | 79 | 53 | 29 | 65 | 42 |
| 4 am | 25 | 42 | 53 | 64 | 73 | 82 | 86 | 87 | 84 | 77 | 51 | 26 | 63 | 42 |
| 7 am | 16 | 26 | 39 | 53 | 66 | 77 | 84 | 81 | 77 | 65 | 30 | 16 | 53 | 42 |
| 10 am | 17 | 30 | 42 | 50 | 64 | 76 | 85 | 81 | 79 | 66 | 38 | 17 | 54 | 42 |
| 1 pm | 19 | 28 | 34 | 44 | 60 | 75 | 86 | 83 | 79 | 65 | 40 | 19 | 53 | 42 |
| 4 pm | 26 | 34 | 37 | 44 | 56 | 74 | 84 | 81 | 77 | 65 | 43 | 25 | 54 | 42 |
| 7 pm | 34 | 43 | 45 | 52 | 62 | 74 | 83 | 81 | 79 | 70 | 51 | 34 | 59 | 42 |
| 10 pm | 32 | 49 | 56 | 62 | 74 | 84 | 89 | 89 | 84 | 78 | 53 | 31 | 65 | 42 |
| ALL | 25 | 38 | 45 | 54 | 66 | 79 | 86 | 84 | 80 | 70 | 45 | 25 | 58 | 42 |
| 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 | 43 | 48 | 57 | 63 | 69 | 73 | 80 | 77 | 62 | 48 | 39 | 40 | 58 | 42 |
| 4 am | 35 | 46 | 56 | 57 | 66 | 70 | 63 | 57 | 56 | 47 | 38 | 34 | 52 | 42 |
| 7 am | 37 | 42 | 53 | 59 | 69 | 67 | 56 | 55 | 54 | 48 | 41 | 33 | 51 | 42 |
| 10 am | 55 | 62 | 64 | 72 | 74 | 73 | 68 | 73 | 75 | 72 | 56 | 50 | 66 | 42 |
| 1 pm | 59 | 62 | 66 | 69 | 65 | 48 | 19 | 27 | 51 | 68 | 58 | 53 | 54 | 42 |
| 4 pm | 60 | 59 | 65 | 64 | 53 | 31 | 8 | 16 | 40 | 63 | 57 | 55 | 47 | 42 |
| 7 pm | 51 | 57 | 69 | 72 | 64 | 46 | 30 | 58 | 80 | 58 | 46 | 49 | 57 | 42 |
| 10 pm | 48 | 52 | 56 | 61 | 63 | 65 | 74 | 79 | 71 | 53 | 48 | 47 | 60 | 42 |
| ALL | 48 | 54 | 61 | 64 | 65 | 59 | 50 | 55 | 61 | 57 | 48 | 45 | 56 | 42 |
| 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 | 61 | 83 | 92 | 91 | 85 | 85 | 94 | 95 | 96 | 96 | 82 | 58 | 85 | 42 |
| 4 am | 58 | 78 | 91 | 93 | 94 | 95 | 98 | 99 | 98 | 96 | 78 | 54 | 86 | 42 |
| 7 am | 51 | 66 | 85 | 89 | 92 | 92 | 98 | 99 | 98 | 91 | 64 | 45 | 81 | 42 |
| 10 am | 50 | 72 | 83 | 88 | 91 | 95 | 99 | 99 | 97 | 93 | 72 | 45 | 82 | 42 |
| 1 pm | 63 | 79 | 84 | 88 | 90 | 94 | 97 | 98 | 98 | 95 | 83 | 57 | 85 | 42 |
| 4 pm | 73 | 83 | 82 | 80 | 78 | 79 | 85 | 92 | 93 | 93 | 88 | 66 | 83 | 42 |
| 7 pm | 77 | 90 | 91 | 84 | 75 | 73 | 83 | 91 | 96 | 96 | 92 | 73 | 85 | 42 |
| 10 pm | 69 | 88 | 92 | 85 | 72 | 69 | 81 | 89 | 93 | 95 | 86 | 63 | 82 | 42 |
| ALL | 63 | 80 | 88 | 87 | 85 | 85 | 92 | 95 | 96 | 94 | 81 | 57 | 84 | 42 |