The French traveler Charles-Jacques Poncet, who visited Sennar near the end of the 17th century, estimated the town had a population of 100,000 inhabitants.

However, when the Dutch explorer Juan Maria Schuver travelled through the town in April 1881, he doubted it had "anything like 100,000 inhabitants, when Khartoum, the centre and capital of a tenfold larger country is not able to muster more than a quarter of that number, if we exclude the garrison.

"[2] He observed that Sennar had declined as trade had over the years shifted to Karkoj, "much more advantageously situated as the terminus of regular navigation, as the natural outlet of the Takruri country between Kassala and Galabat.

[3] In 2011, the Library of Congress still presented maps indicating that Sennar was the capital of Sennar state,[4] but more recent works indicate that the capital is at Sinja.

[5][6] Despite receiving over 400 millimetres or 16 inches of rainfall per year, the extreme heat and high evaporation means Sennar still has a borderline hot arid climate (Köppen BWh) a little below a hot semi-arid climate (BSh).