What is the definition of fortune-telling and why is it forbidden? Does it only relate to seeing the future? There are Hadith which say that the shaitan sometimes is able to steal information from the heaven and pass it down to the fortune-teller. Only it mixes it with a lot of untruths as well.
So, though mixed with untruths could there be some elements of truth in fortune tellers foretelling the future? What about Prophets, pious men or sometimes “gifted” men who have dreams or visions of events in future. Are those acceptable? If so why? Why is weather forecasting not regarded as a form of fortune-telling as it involves predicting the future?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

“Fortune-telling” is a kind trickery used by some people who claim they are able to find out some unseen things.  They claim to know the whereabouts of lost or stolen things, and who stole them, etc.

Fortune-telling is forbidden in Shariah.  It is not based on any scientific or sound evidence.  It is also a false claim to know the unseen.  Allah Says (interpretation of meaning): {Say: "None in the heavens and the earth knows the Ghaib (unseen) except Allâh,….}[27:65].

Fortune-tellers might talk about past or future events.  They sometimes say something that coincides with the truth.  But, most of the time what they say is untrue.  Some of them claim some relation with Jinns.

The geomancer, for instance, claims to know facts by divination using geographic features, figures or lines.

It is unlawful for the Muslim to seek knowledge of unseen things from all types of tricksters or believe in what they say.  Ahmad reported that the Prophet (Sallallahu Alaihi wa Sallam) said: “Whoever comes to a soothsayer or a fortune teller he/she has disbelieved in what was revealed to Prophet Muhammad (Sallallahu Alaihi wa Sallam).”

Jinns used to eavesdrop from Heaven before Prophet Muhammad (Sallallahu Alaihi wa Sallam) was sent.  They used to tell their followers what they overheard.  But when Prophet Muhammad (Sallallahu Alaihi wa Sallam) was sent, they were denied access to Heaven.  So, any Satan which tried to achieve such a mission, after that time was burnt by a blaze from Heaven.  Allah Says (interpretation of meaning): {'And we (Jinn) have sought to reach the heaven; but found it filled with stern guards and flaming fires. 'And verily, we used to sit there in stations, to (steal) a hearing, but any who listens now will find a flaming fire watching him in ambush.}[72:8-9].

As for the Prophets, they are different from other people you mentioned because they receive the true revelation from Allah, The Almighty.  They are infallible and they are entrusted with the Revelation of Allah.  So, we must believe them and abide by what they say.

Finally, dreams can sometimes be true from all people.  But, this does not have any legal impact, as it does not influence the rulings.  As for, weather forecasting, it is completely different as it is based on some natural phenomenon as well as some scientific evidence that are known to specialists in that field.

Allah knows best.