I recommend wearing a helmet and something like a cycling cap or something similar to an Under Armour skull cap that can absorb sweat and protect your head from the sun.
As for your neck, I've always used sunscreen during sunny rides.
Get a bottle that can fit in your saddlebag or backpack, and apply it liberally and as often as necessary.
Sunscreen will protect you from the sun without impeding your ability to move, and it will not be affected by strong winds.
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Definitely do something to protect the back of the neck, and your ears (even with a helmet).
The other area that it seems often "surprises"
you is the backs of your lower legs (though this may be peculiar to the higher latitudes I frequent).
You of course need a sleeved jersey or sun lotion on your arms, and either knee-length pants or sun lotion on the tops of your thighs.
[I'll add that I've several times been on tours with a guy who has "sun allergy", and he does remarkably well in a full-length Tyvek suit.
On hot days when you'd expect him to suffocate, he churns merrily along.]
bicycles.stackexchange.com/users/1584/Daniel R Hicks
Wear sunscreen.
Make sure it has UVA and UVB protection, check the SPF and the UVA star rating (higher numbers means more protection).
Make sure you apply enough sunscreen and reapply it often enough.
There's some fairly detailed information on sunscreen here that you might find useful.
bicycles.stackexchange.com/users/1509/Tom77
Anything wrong with the traditional cycling cap ?
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Solar light cap Oasis or Kayak models do well for sun coverage, while additionally providing evening light power (for the touring).
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I'm preparing for a mini tour in the greek islands this August and I'm getting concerned about sun protection. I'm considering not using a helmet (as I'll reach 30 km/h max). Last year I was wearing a "buff" that protected me from sweat, but did not protect me from minor sunburn. Would a hat be a solution, but of what type (considering strong winds)?
Sun protection while touring
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<touring><health><sun-protection>
bicycles.stackexchange.com/questions/4780
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Cycling in sunny climates requires some special protection. Sunscreen is a must on neck, ears and arms and legs if uncovered. A cap of some kind below the helmet to absorb sweat is a good idea, Under Armour skull cap for example. Instead of using sun cream, the arms and legs can be covered with long pants and long-sleeved top.  Wear clothing that covers your skin or sunscreen on exposed areas. Focus on areas ost at risk — head, ears, arms and tops of thighs. Ensure that your sunscreen has a sufficient SPF rating to protect you.
Wear a helmet and clothing that covers your skin — skull cap, long sleeves and pants, full-length Tyvek suit. Focus on head, ears, arms and tops of thighs. Wear sunscreen on exposed skin, ensuring a sufficient SPF rating to protect you.