A desert in a dream often points to a stretch of life that feels sparse -- low on support, connection, or resources you're used to relying on. It can also reflect endurance, the sense that you're being asked to keep moving through something without much relief in sight. The dream may be naming that scarcity so you can address it directly.
The Moon hath great power in all questions, except when Leo, Capricorn, or Sagittarius ascend: for either of those signs abate of her significations; chiefly Leo or Aquarius. - William Lilly (1602.-1681.)