[Note: The following information does not apply to Algeria, Yemen, Syria, Saudi Arabia, Iraq, and Libya. Each of these countries is a unique situation. As of 2015, travel in these countries is tricky and needs to be handled with care and proper safety measures. At this time we cannot recommend travel to Yemen, Syria, Iraq, Libya or parts of Algeria due to safety concerns. The following also does not apply to Israel and Palestine* since in terms of travel, Israel is more equivalent to Europe, and visiting the West Bank is usually relatively easy. *Based on 2012 UN recognition of the State of Palestine.]
While some Middle Eastern countries (such as Iran, Yemen and Saudi Arabia) require by law that women, citizens and visitors alike, cover their hair, most Middle Eastern and all North African countries do not require women to cover their hair. When traveling throughout the region, you’ll see women with varying degrees of head covering, or sometimes nothing covering their hair. Whether or not a woman covers her hair depends on which kind of Islam she follows.
I’ve met many well-meaning travelers who wear a hijab or other head covering intending to show cultural respect, but unfortunately this is not necessarily how it is perceived by locals. If you’re not a Muslim, wearing a head scarf or hijab can range from confusing to downright disrespectful. Dressing modestly is all that is needed to be respectful. It demonstrates that you respect local customs and culture. (However, note that it is uniformly required to cover your hair with a scarf in mosques.) And remember, just because other tourists are baring it all or running around in a hijab does not mean that it is acceptable and that those around them are not offended.
The only time you will be expected to cover your hair is when visiting mosques, where a lightweight shawl or large scarf will suffice. When visiting mosques it is appropriate to cover most of your hair. A little can be showing at the front, but the back of your hair should be all covered.
Traveling in the Middle East and North Africa, you will see a variety of dress amongst local women — from chic western clothing straight off the streets of Paris to the full-on burqa. How a woman dresses depends on her cultural and religious beliefs rather than any government or cultural requirement (excluding Iran, Yemen and Saudi Arabia, where women are required to cover their hair). Middle Eastern and North African women dress well and tend to be very fashionable.
For women travelers, I recommend pants or skirts with hems below the knees, shirts that cover the shoulders and have a high neckline (no cleavage please) and do not show any midriff. Also no transparent clothing (be careful with whites and sheer fabrics ladies), bra straps showing, and skin-tight clothing. Leave those skinny jeans and crop tops at home; instead opt for looser-fitting, more breathable cotton and polyester. In addition to showing more respect for the Middle Eastern and North African cultures (and thus getting more respect in return) you’ll also be much happier when it is 85F and you’re exploring in the desert.