The sun is directly overhead at 23.5 degrees north latitude on the summer solstice, which occurs around June 21st.

Here's why:

* Earth's Tilt: The Earth is tilted on its axis at approximately 23.5 degrees. This tilt is the primary reason we have seasons.

* Tropic of Cancer: The Tropic of Cancer is located at 23.5 degrees north latitude.

* Summer Solstice: On the summer solstice, the Northern Hemisphere is tilted towards the sun at its maximum angle. At this time, the sun's rays are directly overhead at the Tropic of Cancer.

So, on the summer solstice, the sun is directly overhead at the Tropic of Cancer (23.5 degrees north latitude).