Kaveh Zahedi is the Assistant Director-General of the UN Food and Agriculture Organization (FAO) and Director of FAO’s Office of Climate Change, Biodiversity and Environment. Ko Barrett is the Deputy Secretary-General of the World Meteorological Organization (WMO). Every crop, every animal and every fish has a thermal limit, the point where additional heat stops being normal weather and starts doing damage. In food systems, that threshold arrives sooner than many people realise. For key agricultural species, the danger zone often sits between 25 and 35°C at the moments that matter most, such as flowering and reproduction. As climate change drives more days into the mid-40s°C in major breadbaskets, those limits are already being crossed. The result is lower yields, weaker livestock, stressed fisheries, higher fire risk and farmworkers – the backbone of the system – forced into unsafe conditions. A new joint FAO-WMO report, released on April 22, shows that extreme heat is already cutting production and exposing agricultural workers to dangerous conditions. One analysis found that beef cattle mortality reached as high as 24% in some documented heatwaves. Marine heatwaves were linked to an estimated $6.6 billion loss in fisheries production. And the outlook worsens as temperatures rise. For every 1°C of warming, maize and wheat yields are projected to drop 4–10%. US pressure puts World Bank’s climate plan at risk Adapting to a hotter world will take long-term investment in science, technology and infrastructure if food supplies are to keep pace with demand. We will need more heat-tolerant varieties and breeds, new farming practices, and we will need to make hard choices about what can still be grown as conditions change. But we also need a plan for next season, not just 2100. With more severe heat likely in the coming years and another El Niño poised to test unprepared systems, the priority is to move from crisis response to heat readiness. That starts with early warnings and practical measures to help farmers protect harvests, supply chains and their own safety. Heat warnings farmers can use Weather forecasts should give farmers time to act before extreme heat turns into loss. That is the strategy behind Early Warnings for All, the UN initiative coordinated by WMO with partners including FAO. But early warning only works when reliable observations, modelling and verification turn weather and climate data into forecasts farmers can actually use. Cambodia’s Green Climate Fund-funded PEARL project, supported by FAO, upgraded and installed new weather stations to feed a phone-based app that sends forecasts with crop- and region-specific guidance. When forecasts exceed 38°C, alerts recommend maintaining soil moisture with mulch, shading vegetables, delaying sowing rice seeds, and shifting irrigation to cooler hours. Soda Thai (pictured in a blue T‑shirt) receives training from a Commune Agriculture Officer on how to use the GCF‑funded PEARL Project’s agrometeorological advisory service on her smartphone. (Photo: FAO/Pisey Khun) Soda Thai (pictured in a blue T‑shirt) receives training from a Commune Agriculture Officer on how to use the GCF‑funded PEARL Project’s agrometeorological advisory service on her smartphone. (Photo: FAO/Pisey Khun) That advice is part of a practical set of heat measures that help farmers reduce losses before extreme heat turns into crisis. In some cases, that means shading crops with cloth or solar panels, increasing water storage, installing low-cost cooling misters, or adjusting planting windows. Cattle generate heat when they eat, so feeding them in cooler hours can help. Poultry cannot sweat, so shade is essential. Where extreme heat is becoming the norm, farmers may need to move from cattle to more heat-tolerant goats and sheep, or even switch crops. Evidence from Pakistan shows these adjustments can pay off. A FAO-GCF project field-tested the combination of heat- and drought-tolerant cotton and wheat varieties with mulching and adjusted planting windows. Over six seasons, returns reached as high as $8 for every $1 invested. Extreme heat doesn’t only damage food in the field. It also speeds up spoilage after harvest, turning heat stress into income loss and poorer diets. An estimated 526 million tonnes of food, about 12% of the global total, is lost or wasted because of insufficient refrigeration. In Jamaica, a GCF-funded, FAO-supported programme treats cold storage as climate adaptation, using solar-powered cold storage to help smallholders keep produce market-ready when heat hits. Protecting workers Cold chains and toolkits matter, but they don’t protect the people doing the work. Extreme heat is one of the biggest threats to farmers’ health, driving dehydration, kidney injury and chronic disease, and taxing public health systems in the process. More than a third of the global workforce, around 1.2 billion people, face workplace heat risk each year, with agriculture among the hardest-hit sectors. Mar 19, 2026 Comment Middle East war is another wake-up call for fossil fuel-reliant food systems Much of the world’s food production depends on fossil fuels for fertiliser and transportation, and the crisis in the Gulf will push up prices – and, in turn, hunger Read more Mar 10, 2026 Comment We must invest in early-warning systems to tackle crises like Kenya’s drought With more than 3 million Kenyans facing acute hunger, better mechanisms are needed to help communities reduce devastation from future drought cycles Read more We already know what basic protection looks like, and it is already being put into practice in Cambodia, where the extreme heat advisories are paired with advice for farmers to shift heavy work to cooler hours and ensure access to water, shade and rest breaks. The World Health Organization (WHO) and WMO are calling for the same approach at a wider scale: adjusted work–rest schedules, access to shade and safe drinking water, training to recognize heat illness, and integrating weather and climate information into workplace risk management. Why preparation pays The tools to prepare for extreme heat already exist. The problem is that funding still falls far short of the scale of the risk, and rural communities are too often overlooked by the assumption that extreme heat is mainly an urban problem. In 2023, agrifood systems received just 4% of total climate-related development finance. Without more investment, early warnings won’t reach the people who need them most, extension services will remain under-resourced, and basic protections for crops, livestock and workers will stay out of reach. Preparing in advance is cheaper than absorbing the same losses year after year. It can stabilise production and prices now, while buying time for the bigger scientific and structural shifts agriculture will need in a hotter world. We don’t need a new playbook. We need to use the one we already have. The FAO-WMO report lays out the risks of extreme heat. Now is the time to use that evidence to protect food systems and the people who sustain them. The post Extreme heat is rewriting food security. The best fixes are already within reach appeared first on Climate Home News.