FEWSNET, said over two million Zimbabweans would require food aid between now and March because of the poor rains.
Tens of thousands of Zimbabwean families face disaster this year for the ninth year running.
Rains have fallen in Harare but other parts of the country have had very little.
Only a few areas in the three central Mashonaland provinces have had good rains.
FEWSNET said maize is wilting in eastern, southern and some south-western districts, like Bulawayo and Gwanda.
If the crops fail, few farmers will be able to afford to buy seed and fertilizer to replant.
Aid agencies say funding for food aid is short which could see many people going hungry.