To dream about a harvest suggests you are going to reap the rewards of something you have done previously. For example, you may have worked hard and are now in a position in which finance is not your main concern. Dream harvests can therefore indicate looking back to the past to reap the rewards of the future, but they can also mean looking towards to the future in order to use the wisdom and experience you have gained. The other circumstances in your dream will dictate the interpretation. Much, of course, depends on the quality and quantity of the harvest, but a rich harvest indicates abundance, fruitfulness and fertility.
If you are taking part in a harvest or are attending a harvest festival, this suggests a celebration of your life energy; enjoy it. A poor harvest, on the other hand, may suggest disappointment and disillusionment.