If you're comparing the latitudes of two West and East African capitals, the answer is clear-cut: Conakry, Guinea sits farther north than Addis Ababa, Ethiopia.
That half-degree difference—roughly 55 kilometers (34 miles)—places Conakry closer to the equator's northern fringe. Both cities live in the tropical zone, but Conakry's coastal location on the Atlantic gives it a maritime tropical climate, while Addis Ababa's high-altitude perch (2,355 m / 7,726 ft) on the Ethiopian plateau yields a subtropical highland climate with mild temperatures year-round.
Latitude influences everything from day-length variation and solar intensity to agricultural cycles and building design. Conakry's slightly more northerly position means marginally longer summer days and a touch more seasonal variation in sun angle, though both cities remain firmly tropical.
So, if you're tracing a line across the continent, Conakry claims the northernmost title between the two.