How is it possible to dream of the future?

Your question can be taken in two ways

1 )how it is possible to dream about future 
2) how can dream predict the future 

I assume the second meaning.

    Many societies amd people, believe that dreams can fortell the  future
- and why not? We can make some guesses and estimates  about the future in the 
waking state, and we know that we (our subconsciousness) can solve
real poblems while we sleep.

 This fact is well known and documented, e.g. here
http://www.mindbodysoul.com/corpus/soul/dreams/magical/purpose.html

Most famous example of that is discovery of sterochemistry by Kekule.
http://www.shaalini.com/portfolio/kekule.htm

So, I agree with sfxmystica-ga comment and will expand that a bit:

The search term : Purpose of Dream

brings number of articles which relate to the current topic, e.g. 
http://psych.ucsc.edu/dreams/Articles/purpose.html

In that article psychologists says
".. With the advent of computers, it became fashionable to say that
dreams are "clearing out the software" from a busy day, or that they
are a form of "off-line" processing to save the good stuff and get rid
of the useles .."

I disagree with his too quick of the dismissal of the computer analogy.
There is  such think as 'clearing' - not of the software but of the
memory (called "garbage collection" in computer jargon) but that does not
explains predictive power of dreams. So here is a better analogy betweeen
dream and computer  data processing which does:

This is based on Freud's observation that " .. each dream stand on two legs,
one is some childhood memory, other is a current worry or problem .."

So here is your explanation: During the sleep, our minds does an 'batch job'
searching a vast database of past experiences to find solution to
current issues. The past experiences  are compressed and stored as
associative memory.
All issues related to a particular 'problem area' at 'one spot'. We wake up.
and sometime just our mood has been affected, sometome fragments of coded
memories remain, sometime with a real insight about what is likely to happen.

In wakeful state we need the neurons for real-time processing of
current inputs and cannot spare them for searching the data base.

That's why we dream, and that's how dreams help us to anticipate the future.

Jist a hypothesis, of course :-)

hedgie

Thanks for the answer. It is well thought out and stated, but does not
explain dream predictions of completely unexpected events.

Well, you can think about the future and plan for it whilst you are awake ...

So, you can also do the same thing in your dreams.

I don't believe you can dream of the future, unless you are day
dreaming, of course! :)

When I wake up early in the morning on Sundays and just don't feel
like getting out of bed I go back to sleep. :) Now, invariably it
happens that I dream...
And, sometimes those dreams are quite insightful...

I have a theory for this...

I believe that when I try to go back to sleep again, I don't really go
into the usual deep sleep. Due to this, I believe that our unconscious
or sub conscious part of the mind is able to communicate with our
'conscious' part of the mind through dreams. That is why,

1) We can remember such dreams.
2) They are insightful.

Why are they insightful?

I believe it is because the subconscious part of minds picks up things
that our conscious part misses.

An example : like if you are on a date with your girl or guy and
he/she acts as usual and you guys have a good time. The next morning
you have dream that he/she is dumping you. And that day he/she does
it.
According to my theory - Your unconscious mind might have picked up
the subtle hints through his/her body language ... or something like
that...

What do you think??

While some dream analysts claim some dreams predict the future, my
guess is rather rare confirmation is coincidence and/or adjusted
details of the original dream.   Neil

When you dream the parts of your brain that are responsible for the
logics that you understand from what you have learned in this world
are shut off. The conches mind (you) therefore has fewer recourses to
work with. Often memory access becomes partial or gets mixed up with
other information generated from other brain modules. That is why in a
dream scenarios can become believable, but as soon as you wake up,
they suddenly stop making sense.

As for the ability to predict the future, yes it is possible we only
use 10% of our brain for thinking any way.