Scant rainfall in much of East Africa will lead to low crop yields and increased food prices, the US government's Famine Early Warning System (Fews) predicted in an alert issued on Tuesday.
Poor households will consequently experience greater shortages of food, Fews warned.
"Humanitarians are urged to immediately scale up assistance planning," the alert stated.
Conditions in pastoral areas of Kenya are expected to deteriorate to a phase-three "crisis" level in Fews' five-phase classification of food shortages.
This rating means that acute malnutrition is expected to become more common or that households will likely deplete their essential assets in order to obtain enough to eat.
NEAR FAMINE LEVELS
Parts of Ethiopia and southern Somalia are also forecast to reach crisis stage, with peak needs occurring between July and October.
Northern and central Somalia will meanwhile reach phase-four "emergency" status, which falls one level short of famine on the Fews scale.
Rainfall during the first two and a half months of the March to June long-rains season has been less than 50 percent of average across the Horn, the alert notes.
"Maize harvests are expected to be significantly below average in Kenya's marginal agricultural areas, and harvests are also expected to be delayed by one to two months due to late planting," Fews says.
"Food prices are rising in eastern Uganda and are expected to rise to above-average levels," the alert adds. "In Kenya and Somalia, current low food prices are expected to rise to near to above average levels."
Persistent drought is likewise expected to force distressed sales of livestock in Kenya and Somalia in the coming months.
The current situation is nonetheless better than during droughts in recent years, Fews observes.
"Unlike in 2010/2011 and 2016, ongoing large-scale assistance delivery across the last two years has helped mitigate further deterioration in food security outcomes," the alert observes.
But hunger is still likely to spread far beyond the ranks of current beneficiaries of aid programmes in East Africa, Fews finds.