Olga, Sudan

 SUDAN, Sudan Republic (Gumhuriya al-Sudan), the state in the north-east Africa
In the north-east Sudan washed by the Red m. Most of Sudan - plateau 300-1500 m in the west and south - the height of St. 3000 m.
  In the north - and semi desert in the south - savannah and rainforest. The main rivers - the Nile and its tributaries Sobat and Blue Nile.

Although Sudan lies within the tropics, the climate ranges from arid in the north to tropical wet-and-dry in the far southwest. Temperatures do not vary greatly with the season at any location; the most significant climatic variables are rainfall and the length of the dry season.

From January to March, the country is under the influence of the dry northeasterlies. There is practically no rainfall countrywide

 By early April, the moist southwesterlies have reached southern Sudan, bringing heavy rains and thunderstorms.

 In September the dry northeasterlies begin to strengthen and to push south and by the end of December they cover the entire country. Yambio, close to the border with Zaire, has a nine-month rainy season (April-December)

Temperatures are highest at the end of the dry season when cloudless skies and dry air allow them to soar. The far south, however, with only a short dry season, has uniformly high temperatures throughout the year. Northern Sudan, with its short rainy season, has hot daytime temperatures year round, except for winter months in the northwest where there is precipitation from the Mediterranean in January and February. Conditions in highland areas are generally cooler, and the hot daytime temperatures during the dry season throughout central and northern Sudan fall rapidly after sunset. Lows in Khartoum average 15° C in January and have dropped as low as 6° C

The haboob, a violent dust storm, can occur in central Sudan when the moist southwesterly flow first arrives (May through July). The moist, unstable air forms thunderstorms in the heat of the afternoon. The initial downflow of air from an approaching storm produces a huge yellow wall of sand and clay that can temporarily reduce visibility to zero.