The Forecaster is an orphaned child living under a bridge at 188 Trading Post. He earns caps by selling thoughts to curious travelers passing through. The Forecaster calls the process by which he comes up with his thoughts "thinking" because he is unsure of the origin of his thoughts and is unsure whether he derives his thoughts from a supernatural ability or a very perceptive mind that can digest and make sense of the chatter and movements he sees at the 188. The origins of his thoughts appear to be the massive migraine headaches that he suffers from, which cause his strange and perceptive thoughts to come out. He wears a psychic nullifier which he calls his "medicine". The medicine, he claims, keeps him from thinking about much during the day, causing his thoughts to get bottled up and rush out as soon as it is taken off. Taking his headgear off to think causes him great distress and pain so the amount of "thinking" that he can do for one day is limited.
There is a dialogue option to offer to buy his headgear, but he will refuse the offer. There are also options to "hear his thoughts" on "You," "Here," or "Everywhere," which cost 100 caps each. He is basically a fortune teller. Questioning him about his odd and disjointed collection of pre-War junk will lead him to explain that it's not junk at all, but other peoples' thoughts, because people had to think to make them.
pc On the PC Patch 1, the Forecaster can be seen floating in mid-air a few inches off the ground instead of on the ground in his sitting pose. [verified]
pcps3 If the player has the Mister Sandman perk, visits the Forecaster at night and tries to pickpocket him while he sleeps, he will get the Murder option. However, The Forecaster is a kid and cannot die, but the player still gets the bonus XP. This way you can get unlimited XP points. [verified]