Venezuela's President Hugo Chavez. Photograph: Jorge Silva/Reuters

Hugo Chávez may be wondering, as Venezuela's taps run dry and its cities fall into darkness, whether God is on the side of the Yankees.

The El Niño weather phenomenon appears to be taking sides as it parches leftist-ruled parts of South America and brings bounty to US farmers and corporations. One of the severest droughts in decades has given Venezuela's socialist president a political nightmare as hydro-electrical power dribbles to a standstill, unleashing blackouts, rationing and protests. The waters behind the Guri dam, which supplies more than half the nation's power, have touched perilously low levels. Chávez has declared an "electricity emergency", urging people to spend no more than three minutes in the shower. The president has even dispatched Cuban pilots to seed clouds for rain.

The state oil company Edelca has aimed higher: it summoned workers to a prayer meeting entitled "Clamour to God for the National Electricity Sector".

The crisis has extended to Paraguay, where another leftist leader, Fernando Lugo, ordered the presidential palace lights switched off. In Argentina and Brazil – also with leftist governments – torrential rain and high temperatures have blighted crops with insect and fungi attacks.

A suspicious soul could ask whether El Niño, a Pacific weather system that influences climate worldwide, is on Washington's payroll. Monsanto and Dow Chemical are enjoying booming pesticide and fungicide sales in Argentina as farmers battle to save soy harvests. But in the US Midwest, farmers expect record corn and soy crops.

Venezuela's economy is expected to shrivel as factories close and shops and offices reduce working hours. "It's a true emergency," said Chávez. With his popularity falling, he has fired the electricity minister and brought in foreign experts.

Chávez blames El Niño and climate change. Critics blame the Marxist commandante for not investing enough in power plants during his decade-old revolution. Whether there will be another decade of Chávez could depend on rain.