The affects of the summer Southwest Monsoon are dramatic. On the highland scarp and plateau behind it, lakes are rejuvenated. The vegetation, dormant in late winter, turns green and lush. Springs are re-charged and on occasion flush local wadi systems. These dramatic effects gradually dissipate northwards until the Rub al Khali is reached. How extensive the summer monsoon was during the Neolithic Wet Phase (Early Holocene) has yet to be fully determined, but its presence in the Rub al Khali and beyond has been reported.