The same weather system causing hot sleepless nights in New Zealand is causing famine in other parts of the world.

El Nino is exacerbating severe weather events like floods and droughts in southern and eastern Africa, South America, Asia and the Pacific.

New Zealand aid worker Melany Markham, the spokeswoman for World Vision International's El Nino response said countries like Ethiopia and Indonesia are facing historically severe droughts, which affect their ability to grow crops.

She said subsistence farmers who have just grow enough to eat are only growing enough for half or quarter of the year because food that would normally last 12 months is "maybe lasting three or six."

Ms Markham said aid agencies don't have the resources to respond appropriately and the humanitarian system is really buckling under the strain of the number of crises they're having to deal with.