| YEAR(S) | JAN | FEB | MAR | APR | MAY | JUN | JUL | AUG | SEP | OCT | NOV | DEC | ANN | |||||||||||||
| 1974 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | 48.52 | 38.17 | 30.39 | 23.72 | a | 15.45 | 31.25 | g | ||||
| 1975 | 17.47 | a | 22.25 | 26.03 | 27.73 | 37.68 | 44.97 | 53.68 | 46.26 | 43.27 | 30.00 | 19.93 | b | 17.80 | a | 32.25 | ||||||||||
| 1976 | 14.61 | 22.64 | a | 21.74 | 30.47 | 41.71 | 46.57 | 52.52 | 46.03 | 44.03 | 29.84 | 21.27 | 6.84 | 31.52 | ||||||||||||
| 1977 | 14.21 | b | 20.04 | a | 24.00 | 33.27 | 36.42 | 54.30 | 50.77 | a | 52.00 | 40.93 | 30.83 | a | 23.85 | d | 24.74 | 33.78 | ||||||||
| 1978 | 24.45 | 24.29 | 32.67 | a | 33.37 | c | 36.19 | 43.79 | a | 51.32 | 46.71 | 38.11 | c | 28.13 | 21.21 | a | 7.79 | c | 32.34 | |||||||
| 1979 | 15.75 | c | 21.11 | 26.03 | a | 26.13 | 40.33 | a | 43.52 | e | 52.73 | a | 49.61 | c | 41.93 | 34.55 | b | 20.37 | 16.35 | e | 32.37 | |||||
| 1980 | 24.76 | b | 28.07 | 24.44 | d | 32.33 | 40.50 | k | 43.23 | d | 52.74 | 46.53 | a | 39.00 | b | 29.16 | 25.21 | a | 14.10 | 32.69 | a | |||||
| 1981 | 19.84 | 22.30 | a | 27.45 | 34.30 | 38.32 | 48.57 | 49.52 | 48.73 | a | 43.70 | 26.48 | 26.10 | i | 22.29 | 34.68 | a | |||||||||
| 1982 | 11.73 | a | 22.19 | a | 22.60 | a | 27.31 | a | 38.74 | 45.70 | 52.55 | 48.25 | g | 43.08 | f | 32.53 | a | 26.00 | b | 21.42 | e | 30.08 | b | |||
| 1983 | 20.71 | g | 28.57 | g | 31.68 | c | 30.52 | a | 38.97 | a | 46.80 | 48.48 | 51.55 | b | 43.68 | e | 32.79 | l | 25.21 | p | 26.74 | h | 41.67 | e | ||
| 1984 | 21.07 | c | 18.74 | f | 25.65 | h | 30.50 | d | 40.32 | c | 44.80 | e | 55.70 | a | 52.00 | d | 44.40 | e | 29.32 | i | 25.19 | i | 14.84 | f | 41.26 | e |
| 1985 | 14.95 | i | 16.42 | i | 22.65 | e | 34.63 | 39.31 | b | 51.52 | a | 54.08 | f | 44.93 | d | 36.38 | a | 27.72 | m | 20.00 | l | 16.58 | g | 38.24 | f | |
| 1986 | 22.93 | d | 27.35 | b | 31.07 | c | 33.78 | c | 40.37 | a | 49.00 | a | 49.95 | l | 52.67 | d | 36.46 | f | 26.50 | o | 20.70 | g | 16.97 | 34.27 | d | |
| 1987 | 15.50 | a | 23.32 | 31.07 | d | 33.79 | a | 44.60 | f | 51.41 | c | 52.41 | b | 55.10 | 44.54 | d | 35.38 | b | 28.03 | a | 19.74 | 35.48 | a | |||
| 1988 | 19.82 | c | 18.79 | 25.59 | d | 36.68 | e | 40.64 | c | 56.19 | c | 57.69 | r | 56.00 | c | 42.57 | b | 36.21 | c | 29.27 | 17.03 | a | 34.44 | a | ||
| 1989 | 14.89 | c | 16.91 | f | 33.28 | f | 36.56 | c | 41.96 | c | 50.52 | c | 54.81 | d | 49.15 | d | 44.45 | a | 33.93 | d | 21.30 | c | 12.23 | a | 35.98 | b |
| 1990 | 13.19 | e | 18.36 | 29.55 | 39.82 | h | 41.33 | a | 49.43 | b | 56.30 | d | 55.03 | a | 50.16 | e | 35.39 | 21.63 | 6.33 | a | 34.25 | a | ||||
| 1991 | 14.29 | c | 24.86 | 30.46 | c | 32.04 | c | 37.52 | b | 44.60 | 56.35 | 56.22 | h | 44.23 | 36.26 | 26.43 | b | 16.07 | a | 33.01 | a | |||||
| 1992 | 16.52 | 27.59 | b | 31.33 | a | 38.92 | f | 47.21 | c | 50.52 | c | 55.16 | 54.34 | b | 44.79 | a | 38.26 | 21.23 | d | 15.43 | a | 36.58 | a | |||
| 1993 | 17.32 | 25.88 | c | 35.32 | 35.52 | e | 44.23 | 44.48 | a | 50.60 | a | 49.40 | a | 41.97 | 37.26 | d | 18.03 | 19.29 | 34.94 | |||||||
| 1994 | 16.77 | 20.35 | b | 29.27 | a | 37.40 | e | 44.84 | 48.90 | a | 58.94 | 51.45 | 42.77 | d | 32.50 | c | 22.31 | a | 23.38 | b | 35.74 | |||||
| 1995 | 29.67 | a | 27.57 | 29.68 | 32.92 | e | 41.85 | e | 45.46 | b | 52.97 | 51.06 | 44.90 | 32.77 | a | 27.67 | 25.81 | 36.86 | ||||||||
| 1996 | 25.58 | 28.97 | 28.03 | 33.47 | 42.07 | d | 48.93 | 57.16 | 51.42 | 41.00 | 34.35 | 25.90 | a | 25.34 | b | 36.85 | ||||||||||
| 1997 | 24.13 | a | 25.32 | 28.79 | c | 34.72 | e | 44.00 | b | 49.23 | 53.81 | 53.03 | 47.03 | 32.92 | e | 26.73 | 16.03 | 36.31 | ||||||||
| 1998 | 25.77 | 28.44 | a | 29.55 | 30.80 | 37.87 | a | 47.67 | 56.39 | 52.52 | 50.60 | 32.29 | 28.28 | e | 15.84 | 36.33 | ||||||||||
| 1999 | 21.37 | d | 26.22 | a | 25.57 | a | 33.96 | d | 40.61 | c | 48.90 | 55.06 | 53.04 | d | 43.77 | 32.59 | i | 25.73 | 14.84 | 35.37 | a | |||||
| 2000 | 25.65 | 30.89 | b | 28.74 | 35.37 | 43.65 | 52.30 | 54.16 | ----- | z | 43.34 | a | 32.67 | a | 20.67 | c | 19.05 | i | 36.74 | b | ||||||
| 2001 | 16.71 | x | 21.07 | 31.00 | 32.97 | a | 45.66 | b | ----- | z | 53.17 | s | ----- | z | ----- | z | 31.52 | h | 25.76 | a | 25.13 | a | 30.26 | f | ||
| 2002 | 17.54 | c | 20.40 | c | 23.00 | c | 31.36 | h | 36.92 | f | 50.80 | e | 58.93 | c | 53.57 | h | 44.14 | b | 28.19 | d | 22.22 | g | 22.59 | d | 33.20 | d |
| 2003 | 27.85 | e | 16.27 | f | 24.58 | g | 30.74 | k | 40.65 | h | 48.82 | h | 60.96 | g | 53.73 | e | ----- | z | ----- | z | ----- | z | ----- | z | 40.79 | j |
| 2004 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 2005 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 2006 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 2007 | 4.47 | l | 22.36 | n | 26.81 | j | 33.05 | j | ----- | z | 49.76 | e | 61.88 | f | 56.79 | c | 43.00 | g | 31.88 | n | 24.20 | j | ----- | z | 53.27 | j |
| 2008 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | 45.20 | t | ----- | z | ----- | z | 42.83 | a | 32.48 | b | 26.96 | c | 15.70 | d | 29.49 | h |
| 2009 | 17.65 | h | 22.56 | j | 23.27 | p | 31.24 | e | 47.14 | b | 50.80 | e | 56.96 | d | 51.24 | j | 46.20 | j | 33.71 | ----- | z | ----- | z | 43.97 | g | |
| 2010 | ----- | z | ----- | z | ----- | z | ----- | z | 36.19 | 49.40 | 55.57 | j | 50.11 | m | ----- | z | ----- | z | ----- | z | ----- | z | 42.80 | j | ||
| Period of Record Statistics | ||||||||||||||||||||||||||
| MEAN | 19.72 | 24.09 | 27.97 | 32.76 | 40.93 | 48.40 | 54.00 | 51.06 | 43.21 | 32.66 | 24.06 | 17.48 | 34.48 | |||||||||||||
| S.D. | 5.05 | 3.52 | 3.55 | 2.84 | 3.18 | 3.24 | 2.75 | 3.27 | 3.17 | 3.01 | 3.15 | 5.47 | 2.08 | |||||||||||||
| SKEW | 0.29 | 0.13 | -0.10 | -0.63 | 0.36 | 0.24 | -0.04 | -0.20 | 0.16 | -0.16 | -0.12 | -0.33 | -0.18 | |||||||||||||
| MAX | 29.67 | 30.89 | 35.32 | 37.40 | 47.21 | 56.19 | 58.94 | 56.79 | 50.60 | 38.26 | 29.27 | 25.81 | 36.86 | |||||||||||||
| MIN | 11.73 | 18.36 | 21.74 | 26.13 | 36.19 | 43.23 | 48.48 | 44.93 | 36.38 | 26.48 | 18.03 | 6.33 | 31.52 | |||||||||||||
| YRS | 26 | 24 | 26 | 26 | 27 | 30 | 25 | 26 | 27 | 25 | 24 | 26 | 11 | |||||||||||||