Why do I get a headache whenever I step out in the sun? Eyesight is normal but still!

If you feel headaches only when you are under the sun, they might be 'heat-induced headaches', most probably they aren't due to any underlying disease. It may occur if you are dehydrated. Dehydration can trigger both a headache and a migraine. It can last for up to 3 hours.

You can avoid such situations if you,

Care to stay hydrated
Use Sunglasses
Take regular breaks in shaded areas
Wear fragrance-free sunscreen or other lotions