Why does a sunburn generate you sooooo sleepy for days?

Why does a sunburn generate you sooooo sleepy for days?
Dehydration, sunburn depletes the body of fluids and until they are replaced the body goes into 'shut down' mode. Make sure you hold plenty of water and wet based fluids so as to rehydrate yourself.
Soak within a luke warm hip bath with a suitable dose of bicarbonate of soda will help the adjectives skin and cool it down.
Getting sunburnt is not a clever thing to do as it sooooo increases the risk of melanoma cancer.
Here contained by Australia we have a rhyme for going out contained by the sun;
"Slip, Slop, Slap", slip on a shirt, slop on some sunscreen (30+) and slap on a hat".
And Ouch! I have be sunburnt too many times to fail to remember the pain.
Its because within order to carry sunburn you have to be surrounded by the sun for awhile and that just tires your skin out. and your in one piece body
Your skin is the largest organ of your body. When you burn a large portion of it your body have to focus a lot of it's energies toward uplifting it.