Climate
Adamawa has a tropical climate characterised by dry and wet seasons. Local variations originate from the peculiar meteorological and geographical influence of the area in question. The dominant features of the rainfall in Adamawa State are its seasonal character, its variability from year to year and the intensity of the rainfall or the large energy content of the rainfall and ends later October, while the dry season lasts from November to March. The average rainfall for the state is 759mm in the northern parts and 1,051mm in the southern parts around Ganye and Jada Local Government Areas.

The wettest months are August and September. The length of the rainy season averages eighty-five to ninety-two days per year. Evapotranspiration exceeds rainfall for most parts of the year. There is one primary rainfall peak each year. This occurs between June and September when the mean monthly rainfall is 198mm.

Humidity and Temperature:

Federal Secretariat Complex Main Gate, Jimeta, Yola

The surface air, at the beginning of the dry season in November, is very hot. The season starts with a marked and abrupt drop in the moisture content of the surface air followed by a change in the direction of the sur- face winds. The relative humidity drops abruptly from eighty-two to ninety-two per cent between June and October (average at 10a.m.) to about twenty-five to thirty-six per cent between December and March. Daily minimum temperatures normally drop more rapidly than the maximum.

Consequently, the diurnal range of temperature increases rapidly. Daily maximum screen tempera- tures in November may rise as high as 33°C and the minimum may fall as low as 11°C. The sky is mostly clear in November and this permits longer hours of sunshine. The average duration of sun- shine in November varies from 10.6 to 9.2 hours.

Harmattan

The harmattan period is experienced between December and February. The sea- son is characterised by very strong and cold desiccating and dust-laden winds. Trees shed their leaves during this period, grasses die out entirely and are burnt off. Visibility is generally reduced. The extremely dust-laden atmosphere shuts out insolation and leads to low temperatures.

The Police Roundabout, Jimeta

The thickness of this haze and dust layer of the harmat- tan exceeds a height of 1500 meters. This appears like a dense fog and gives the day a dull and gloomy look. Very little direct insolation can reach the ground on such days and consequently the daily maximum temperatures become lower. Dense harmattan dust rarely lasts continuously for more than four or five days even during the peak of the harmattan season.

The frequency of occurrence of such dense harmattan dust varies from year to year. The principal characteristics of the harmattan are: (i) The generally north-easterly direction of the winds; (ii) Low atmosphere moisture content; (iii) A large diurnal range of temperature; and (iv) Absence of convective type of cloud. Apart from the harmattan, the prevalent winds consist of the north-east and south-east trade windsduring the dry and wet seasons respectively, Wind speeds range from 115km per day in April/May to 42km per day between August and September.