The UN in Haiti says 1.5 million people remain at risk of not having proper access to food in 2013 due to the destruction caused by Hurricane Sandy and other natural disasters.
The situation has been made worse by a drought earlier this year, it says.
At least 54 people died as Hurricane Sandy hit the impoverished Caribbean nation two weeks ago.
The country is still struggling to recover from a devastating earthquake in January 2010.
During the spring and summer of this year, rural households in northern parts of Haiti were badly hit by drought.
Then, Tropical Storm Isaac caused extensive damage in August.
Two months of heavy rain followed before Haiti was hit by Hurricane Sandy on 23 October.
An estimated 21,000 people were left homeless by the hurricane, which also destroyed at least 70% of crops of yam, corn and banana in the south of the country.
The UN's World Food Programme says many areas remain isolated.
The Haitian government and the WFP have now appealed for an extra $39m (£24m) to continue distributing food, to rehabilitate agricultural land and for flood control.
It has continued to rain heavily in most of Haiti since the hurricane.
Floods in the country's second biggest city, Cap-Haitien, left at least 20 people dead last week.
"We didn't even have anything. And now, we have lost everything," Rochenel Cineus, a Cap-Haitien resident told the AFP news agency.
The father of three has been sleeping in the streets with his family since Thursday night.