The latitude of the tangent rays in the Southern Hemisphere ranges between 66 1/2 and 90 degrees south. The latitude of the tangent ray depends on what day of the year it is.
The tangent rays are lines representing rays of sunlight that just barely touch the edge of the round disk of the Earth as seen from the sun. During the spring and fall equinoxes, the sun is directly overhead at the equator and the tangent ray in the Southern Hemisphere is at 90 degrees south. During the summer and winter solstices, the tangent ray in the Southern Hemisphere is at 66 1/2 degrees south.