July 2026 THI Summary

July has been another exceptionally hot month across the UK, with consistently high THI levels affecting dairy cattle in all regions. The prolonged periods of high THI have significantly reduced opportunities for cows to cool down overnight, increasing the risk of heat stress and its impact on health, welfare, and productivity.

Key Observations

A Hot Start to July

July got off to a very hot start, with all regions across the UK recording THI levels above 81. Although the North experienced some cooler spells later in the month, the South remained under sustained heat stress, with average THI levels rarely dropping below 68.

Sustained Days at High THI

Many areas of the UK experienced prolonged periods of high THI throughout July. These extended spells of heat reduce the opportunity for cows to cool down overnight, leading to a build-up of heat stress over several days. Keeping fans running overnight during these periods can help cows recover more effectively and be better prepared for the following day’s heat.

The Long-Term Impact of Heat Stress

The effects of heat stress can continue long after temperatures have dropped. During hot weather, cows spend more time standing and less time lying down as they try to keep cool. After several weeks of elevated THI, this extra standing time can increase pressure on feet. As we move into late summer, farms may begin to see an increase in foot lesions and lameness cases because of the challenging conditions experience during summer.

Regional Heat Stress Trends

South of England

The South was once again the hottest region this month. During July, 60% of all hours were spent above a THI of 67, and every day recorded THI levels above 65. With a monthly average THI of 69, many cows will have been experiencing heat stress for prolonged periods, with very little opportunity to recover between heat events.

Midlands

Conditions were slightly cooler than those seen in the South, but the Midlands still experienced sustained periods of heat stress. 25 out of 31 days recorded THI levels above 65, while shed temperatures reached as high as 34.6°C. During hot weather, it is important to manage temperatures inside buildings by maximising natural ventilation and using mechanical ventilation where needed, helping to keep internal conditions as close as possible to that external. 

Wales

Wales experienced THI levels above 65 on more than half of the days in July. The region also recorded the highest 24-hour average THI of regions, reaching 76. This highlights the challenge cows faced, with little relief from heat stress during both the day and night. 

North of England

Although the North benefited from some cooler spells throughout the month, it still recorded the second-highest THI value of all regions, reaching 84. The region’s average THI for July was 66, showed regular periods of heat stress. However, cooler days and overnight temperatures provided cows with more opportunities to recover compared with regions further south. 

Scotland

Scotland recorded the lowest average THI during July, but that does not mean cows avoided heat stress. Shed temperatures still reached 32.1°C, corresponding to a THI of 83. Unlike other regions, Scotland experienced greater fluctuations in temperature and humidity. While periods of high THI were generally shorter, cows were exposed to sudden changes in conditions, making it more difficult for them to adapt and maintain comfort.

Managing heat stress

There is no silver bullet for reducing heat stress, and most of the key principles will already be familiar. The challenge is often getting the basics right and looking for small wins that can make a big difference during warm weather.

• Water is the easiest place to start. Is there enough water space in the shed, and could more be provided? Ensure troughs are clean, supplied with fresh water, and have adequate flow rates so cows can drink easily when demand is highest.
• Airflow is equally important. Carry out a smoke test to assess ventilation. Smoke should move freely out of the building rather than linger. Make sure side inlets are open and that the ridge is functioning effectively to promote natural air movement.
• Lighting can also influence cow behaviour. Bunching is a common issue during summer, and cows will often gather in darker areas of the shed because they associate them with shade, even when they are not actually cooler. Uniform lighting throughout the building can help reduce this behaviour.
• Roof lights can create significant solar gain and result in localised hot spots. Monitor for areas where direct sunlight is causing excessive heating and consider covering roof lights where necessary.

Finally, consider mechanical ventilation. Increasing air speed over the cows’ backs can significantly improve cooling. Systems should be positioned to deliver consistent, even airflow throughout the shed, ensuring all cows benefit rather than just those in specific areas.

You might be interested in our blog giving Practical Tips on Managing Heat Stress.

Get in touch if you need support with managing heat in your herd.