Be careful while out in the sun! Too much of a good thing can lead to sunburn.
We all need some sun to keep vitamin D levels up to our bodily needs. But it should never be overly done to the point where we burn our skin. In the instances where you see a change in skin tone it is likely that your skin has been damaged to the point where it is skin burn.
Remember that your skin may take a couple of hours to show signs of reddening and it might be too late to avoid the pain & misery of sunburn from too much sun! If you do notice a change in skin color or excess heat in your skin, get out of the sun immediately. Also, to avoid sunburn be sure to use a high value sun screen in all cases and refresh the application if you are out in the sun for extended periods. It is also wise to wear as much protective clothing as you are comfortable with. Be sure to watch for signs of heat stroke or exhaustion (dizziness, headache or feeling ill), take a cool bath and drink plenty of liquids to remain hydrated.. In case of a severe sun burn it may be cause for hospital treatment.