Calling the crisis "the worst ... in 10 years", IFRC secretary general Bekele Geleta said: "After March, it could be a famine situation".
"Usually, people start responding when they see emaciated children on their screens. If assistance is not given, in a few months, they could start seeing that, there could be famine," due to poor harvest because of drought and high food prices, he said.
The IFRC will launch an appeal late next week to assist one million needy people, of which 600,000 live in Ethiopia, and the rest in Djibouti, Kenya and Somalia.
Geleta said 80 to 100 million Swiss francs (52 to 65 million euros, 67 to 83 million dollars) were needed for the IFRC operation in the region.
Speaking on the sidelines of UN climate talks in this Polish city, Geleta said global warming was "definitely" a contributing factor to the crisis in the Horn of Africa.
"What we are seeing in the Horn is floods and droughts and the frequency has increased enormously," he said.
"New areas that did not know droughts and floods are being affected now. It may not be conclusive, but definitely it is a contributing factor."