Twice a year the noon Sun passes almost straight overhead in Lagos. For a few minutes around solar noon, upright poles, people and buildings cast almost no shadow.
Nigeria · Gulf of Guinea · ~6.5°N · 6.52°, 3.38°
Times are solar noon in Africa/Lagos (UTC+1), rounded to the minute.
Earth's axis is tilted 23.44°, so through the year the place where the noon Sun stands straight overhead moves north to 23.44° N in June and back south to 23.44° S in December. It crosses Lagos (6.5° N) twice: once on the way north and once on the way south. Only places between the tropics ever have the Sun straight overhead.
Why seasons happen: axial tilt explained
The next zero-shadow days in Lagos are Tuesday 6 April 2027 and Monday 6 September 2027. At solar noon (12:49 GMT+1 and 12:45 GMT+1, Africa/Lagos) the Sun is 0.1° and 0.1° from straight overhead.
It is a day when the noon Sun stands almost straight overhead, so a vertical pole or a standing person casts almost no shadow for a few minutes. It happens only between the Tropic of Cancer and the Tropic of Capricorn, twice a year, on dates set by the latitude.
The noon Sun moves north and south through the year, and it is overhead where its path crosses the latitude. Places near the equator get their zero-shadow days close to the March and September equinoxes; places near the tropics get them closer to the solstice. Lagos is at 6.5° N.
Stand a straight stick or a bottle upright on level ground in the sun and watch it around solar noon: its shadow shrinks to almost nothing and sits right at its base. Look at the shadow, never at the Sun.
Other towns: Accra · Kampala · Windhoek · Nairobi · Addis Ababa · Dar es Salaam