Historically, October through March offered the most comfortable conditions — desert temperatures drop to manageable levels and the site is pleasant to walk. The summer months (June–September) bring extreme heat that makes an exposed hilltop ruin punishing to visit.
Since 2015, Yemen has been in civil conflict and the Jawf region has seen active fighting. Travel to Yemen is not advisable at present. Check the latest advice from your government's foreign travel authority before making any plans.