Number of days available for climatic review
| Parameter | Jan | Feb | Mar | Apr | May | Jun |
| Tmax | 1107 | 1039 | 1145 | 1105 | 1142 | 1096 |
| Tmin | 1111 | 1036 | 1139 | 1105 | 1138 | 1095 |
| Duration of sunshine | 275 | 277 | 306 | 323 | 274 | 260 |
| Precipitation | 157 | 143 | 157 | 154 | 157 | 150 |
| Humidity/Visibility | 151 | 138 | 151 | 144 | 149 | 144 |
| Parameter | Jul | Aug | Sep | Oct | Nov | Dec |
| Tmax | 1143 | 1142 | 1120 | 1154 | 1125 | 1171 |
| Tmin | 1135 | 1142 | 1118 | 1153 | 1135 | 1174 |
| Duration of sunshine | 332 | 241 | 349 | 299 | 265 | 298 |
| Precipitation | 158 | 160 | 182 | 185 | 180 | 186 |
| Humidity/Visibility | 150 | 151 | 170 | 170 | 171 | 180 |
Climate data is usually derived from meteorological data of a certain number of years. The actual number of recorded years may vary from only a couple to 50 years or more. The quality of climate data depends on the number of available recorded years. Fewer years means less reliable data. The standart-period for reliable climate data is 30 years. For example, the mean monthly temperature for, let's say January, would ideally calculated from a total number of 930 recorded January-days. However, the usual number of recorded days is much smaller. The table above shows the actual number of recorded days for every parameter measured. |
Alor Setar