Dry/Wet Season Dates

The question of when dry season and wet season begin depends where in Panama you are looking. Bocas del Torro, for example has a very different seasons than the Panama Canal Area. Even within the Canal Area, the northeastern region has a somewhat shorter dry season than Panama City.

The dry/wet season dates also depend on what metric you choose to use to define the seasons. A number of different metrics have been tried over the years and all of them tend to have their advantages and disadvantages. All of these metrics are, to some extent, subjective and open to interpretation.

The T-ESP has adopted the metric used by the Panama Canal Authority. The ACP uses a metric that tracks 11 variables. The metric definition can be found by clicking here.
Dry Season
Length of Season
Year Begin date Day of year End Date Day Dry Wet
1954 25-Dec-53 359 05-May-54 124 131 236
1955 27-Dec-54 361 02-May-55 121 126 275
1956 01-Feb-56 397 02-May-56 122 91 231
1957 19-Dec-56 354 12-May-57 131 144 223
1958 21-Dec-57 355 30-Apr-58 119 130 229
1959 15-Dec-58 349 15-May-59 134 151 234
1960 04-Jan-60 369 12-Apr-60 102 99 247
1961 15-Dec-60 350 11-May-61 130 147 231
1962 28-Dec-61 362 11-May-62 130 134 228
1963 25-Dec-62 359 25-Apr-63 114 121 213
1964 24-Nov-63 327 22-Apr-64 112 150 224
1965 02-Dec-64 337 08-May-65 127 157 231
1966 25-Dec-65 359 13-Apr-66 102 109 257
1967 26-Dec-66 360 26-Apr-67 115 121 231
1968 13-Dec-67 347 27-Apr-68 117 136 229
1969 12-Dec-68 347 16-Apr-69 105 125 248
1970 20-Dec-69 354 26-Apr-70 115 127 239
1971 21-Dec-70 355 30-Apr-71 119 130 213
1972 29-Nov-71 333 30-Apr-72 120 153 239
1973 25-Dec-72 360 17-May-73 136 143 212
1974 15-Dec-73 349 02-May-74 121 138 226
1975 14-Dec-74 348 03-May-75 122 140 227
1976 16-Dec-75 350 20-May-76 140 156 185
1977 21-Nov-76 326 17-May-77 136 177 217
1978 20-Dec-77 354 13-Apr-78 102 114 244
1979 13-Dec-78 347 16-Apr-79 105 124 252
1980 24-Dec-79 358 05-May-80 125 133 244
1981 04-Jan-81 370 12-Apr-81 101 98 273
1982 10-Jan-82 375 09-May-82 128 119 189
1983 14-Nov-82 318 12-May-83 131 179 222
1984 20-Dec-83 354 22-May-84 142 154 199
1985 07-Dec-84 342 06-May-85 125 150 222
1986 14-Dec-85 348 20-Apr-86 109 127 240
1987 16-Dec-86 350 25-Apr-87 114 130 235
1988 16-Dec-87 350 25-May-88 145 161 209
1989 20-Dec-88 355 14-May-89 133 145 214
1990 14-Dec-89 348 04-May-90 123 141 223
1991 13-Dec-90 347 01-May-91 120 139 226
1992 13-Dec-91 347 18-May-92 138 157 217
1993 21-Dec-92 356 25-Apr-93 114 125 243
1994 24-Dec-93 358 16-May-94 135 143 200
1995 02-Dec-94 336 01-May-95 120 150 271
1996 27-Jan-96 393 07-May-96 127 101 255
1997 17-Jan-97 382 07-Jun-97 157 141 185
1998 09-Dec-97 343 29-May-98 148 171 234
1999 18-Jan-99 383 03-May-99 122 105 259
2000 17-Jan-00 382 10-May-00 130 114 245
2001 10-Jan-01 376 26-May-01 145 136 237
2002 18-Jan-02 383 21-May-02 140 123 201
2003 08-Dec-02 342 05-May-03 124 148 238
2004 29-Dec-03 363 24-Apr-04 114 117 234
2005 14-Dec-04 349 06-May-05 125 143 252
2006 13-Jan-06 378 28-Apr-06 117 105 235
2007 19-Dec-06 353 26-Apr-07 115 128 251
2008
02-Jan-08
367
             
Avg.
 15-Dec 349.9 01-May 121.8 132.4 227.2
S.D.
15.9
12.6 19.8 20.2
Median
 20-Dec 354 03-May 123 135 231

Metric for Calculating Season Dates

The beginning and end dates of the Panama Canal watershed dry season as defined by the Meteorological and Hydrological Branch of the ACP uses a metric that tracks 11 variables (see list below). There are no publications justifying the use of this system and any questions should be directed to Mike Hart of the Meteorological & Hydrological Branch of the Panama Canal Authority at: EIEH-MET@pancanal.com

 

Westerly Component of 300 HPA Wind

Gatun Lake Basin evaporation > 0.13" day-1

Sea temperature at Amador < 80 °F

< 5 grams of  water vapour kg-1 below 12,00 ft

Temp-Dew point difference SFC-400 HPA., > 10°C

Howard Airforce Base wind speed SFC-4000 ft., > 15 knots

Inter-Tropical Convergence Zone > 2 deg. Lat. south of  Panama

Pacific Coast sea breeze < 2 hours day-1

Atlantic Coast surface wind average > 6.0 M.P.H.

Gatun Lake level (corrected for water usage) falling

Gatun Watershed daily rainfall average (of 26 stations) < .25"