II. Seasonal Climate of the Abay (Nile) Basin
Source (Encyclopedia Brittanica: Nile River)


Almost no area within the Nile basin experiences a uniform type of climate, equatorial or Mediterranean. While the Nile basin in Sudan and Egypt remains rainless during the northern winter(July - August), its southern parts and the highlands of Ethiopia experience heavy rain--more than 60 inches (1,520 millimetres)--during the northern summer(July - September). Most of the region falls under the influence of the northeast trade winds between October and May, which causes the prevailing aridity of most of the basin.
1. Southern Sudan, Lakes Region, Ethiopia
Dry Season:
October - June - Ethiopia
November - March - Lake regions
December - February - South Sudan
Rel. Humidity 80%
Mean Temperature 80F(27C)
Rainy Season :
July - September - Ethiopia
April - October - Lake regions
March - Novemeber - South Sudan
Rainfall 50 in. Rel. Humidity 80%
Both peaking in August
Mean Temperature 60F(16C)

Tropical climates with well-distributed rainfall are found in parts of the East African lakes region and southwestern Ethiopia. In the lakes region there is little variation throughout the year in the mean temperature and humidity, ranging from 60-80F or 16-27C and 80 % respectively varying with location.

2. Central and Northern Sudan,Al Jezirah( region between T'Kur Abay and Nech Abay)
Dry season
Dec - February
Mild, Cool
Minimum temperature
occurs in January
Dry Season 2
March - June
Hot, Dry
Max temperatures reaching
up to 105F(41C) in May or June
Rainy Season
July - Oct
Wet, Hot
Rains July and August

The rainy season gets shorter, rainfall decreases, and is confined to July and August in the northern part of central Sudan. Three seasons may be distinguished. The first of these is the pleasant, cool, dry winter, which occurs from December to February; this is followed by hot and very dry weather from March to June; and this is followed, in turn, by a hot rainy period from July to October.

North of Khartoum less than 5 inches of rain falls insufficent to sustain life permamnently, while 10 inches fall in the Al Jezirah region between the two niles.
In June and July the central parts of The Sudan are frequently visited by squalls of 2-3 hours duration, called Haboobs, carrying large quantities of sand and dust.

3. Northern Sudan, Egypt, Mediteranean
Rainy Season
November - March - Egypt only
Arid , Dry Atmosphere - Northern Sudan
Daily Max Temp(Cairo) - 68-75F(20-24C)
Night Minimum 50F(10C)
8 in. on the Coast, Less than 1 in. in Upper Egypt
Dry Season
Temperatures Surpass 100F(38C)
April - December - Egypt
Avg Daily Maximum (Aswan) 117F(47C)
Arid Dry Atmosphere

A desert-type climate exists over most of the remainder of the area north to the Mediterranean. Northern Sudan and the desert of Egypt are arid, with dry atmosphere, and a considerable seasonal, as well as diurnal, temperature range in Upper Egypt. Winter temperatures decrease to the north. During the Spring, from March - June, depressions from the Sahara or along the coast travel east, causing dry southerly winds, which sometimes results in a condition called khamsin. These are sandstorms or dust storms during which the atmosphere becomes hazy; persist sometimes for three or four days, at the end of which the phenomenon of a "blue" sun may be observed.