The location of Jesus’ baptism was a tributary of the Jordan River near Jericho, just north of the Dead Sea. Jericho is an oasis, but the area around it is part of the Judean Wilderness.
Jerusalem weather is actually not so bad. The humidity hovers around 50%, which is nice, and it’s always cool at night with breezes blowing in from the Mediterranean Sea. That is, except for about 50 days each year when there is a sharav or hamsin. This is when the winds turn and come in from the Arabian Desert to the southeast. Then the air is dry, dirty, and hot.
Jerusalem is very hilly and not very lush, but when you go over the hills to the south or east, you are in a desert wilderness, the Judean Wilderness. This wilderness is not as dry as are the Arava or the Negev, even farther south, but wilderness, still.
Most of the land around the baptism site is wilderness. Oases can provide water, but Jesus spent 40 days fasting and praying, receiving revelation for His ministry. When the Bible uses the number 40, it’s a saying that means “a long time.” So we don’t know exactly how long Jesus prayed and fasted, but it was beyond human ability to endure.
Bein Harim in the Judean Wilderness