The hills were filled with lush green hues several months back, but as farmer Derek Tan looks at his 4ha fish and vegetable farm in Broga in southern Selangor, brown patches of soil occupy spots where leafless vegetation lies.

"Our water sprinklers are working harder than usual, but still the heat is too much to bear - vegetables are just not growing fast enough," Mr Tan told The Straits Times.

The farm, located at the edge of a forest, is lucky as it is still able to source fresh water from its ponds to keep its soil moist - a feat that would leave many farmers in envy. The ponds had water piped into them from a nearby stream.

A heatwave in South and Southeast Asia is hitting the region's crops and livestock as the cyclical climate phenomenon known as El Nino absorbs tropical countries' sources of water.

In Malaysia, farmers are staring at a prolonged dry season, topped with escalating temperatures that are hitting 40 deg C.

As dams dry up, the Malaysian authorities say some states have reduced the release of water to be treated at plants and piped to homes.

The drought is expected to last until June and may even drag on till September, with rainfall decreasing by between 20 per cent and 60 per cent.

The authorities are rationing water in the worst-affected areas while schools had closed in several districts in Pahang and Perlis.

The levels of water in some rivers and dams have dropped sharply throughout Malaysia.

High temperatures have also brought back the haze temporarily as swathes of land with peat areas in Selangor's Sepang and Kuala Langat caught fire.

Most farmers still rely on natural sources of water such as rivers to minimise costs, and with the heat rising, they can only hope that these water sources keep flowing.

In the north, Kedah and Penang padi farmers do not have enough water to begin planting their lands, as water from the dams is not being released downstream in sufficient volumes.

"We are already providing shade and more water for vegetables to grow, besides that it's beyond our control," said Mr Alen Lee, Mr Tan's business partner.

Singapore imports most of its vegetables, fruits, poultry and hen eggs from its neighbour, Malaysia. In 2015, official figures show Singapore imported 41 per cent, or 224,800 tonnes, of its vegetables from Malaysia. The island nation imported 36 per cent of its fruit supply, 42 per cent of its poultry and 76 per cent of its eggs from Malaysia last year.

Production in farms is already on a decline, as Mr Lee saw his daily crop collection fall by 40 per cent despite having four fish ponds doubling up as fresh water reserves for the vegetables. Agriculture and Agro-based Industry Minister Datuk Seri Ahmad Shabery Cheek said on Thursday that the hot weather would reduce Malaysia's chicken egg production by 5 per cent to 10 per cent, stemming from farmers who still operate open farms instead of temperature-controlled indoor ones.

Exports of Malaysian meat and seafood to Singapore already declined from January to February this year, Singapore government statistics show, as temperatures slowly climbed above historical averages.

Rising heat has also spiked electricity usage, as Peninsular Malaysia recorded its highest demand on Wednesday, according to national utility firm Tenaga Nasional.

But it is not just residents who are cranking up the air-conditioning at home, as livestock farmers are switching on fans to keep animals cool.

"We live in hot and humid weather, it's unavoidable, so you have to be willing to spend on (the) electricity bill to get the water pump and fans working," said Mr Chung Hock Meng, a pig farmer in Tanjung Sepat, a coastal town in Selangor's south-west.