Zambia's President Levy Mwanawasa has declared a national disaster and appealed for international food aid.
Maize stocks are low across southern Africa
More than one million Zambians face severe food shortages due to drought. Last week, Zambia appealed for $18m in aid to deal with the food crisis.
Zambia is one of six countries across southern Africa facing a food crisis. The UN says some 12m people in the region need food aid.
Malawi is worst hit. It declared a national disaster last month.
Zambian MPs passed a resolution urging the government to declare a national disaster last week.
Some four million people need aid in Zimbabwe, along with hundreds of thousands in Lesotho, Mozambique and Swaziland, according to the World Food Programme.