The UK's Met Office has issued its highest heat alert—a Red Warning—as temperatures are expected to peak around 39°C in southern England on Wednesday and Thursday, 26–27 June 2026. That would break the UK's June temperature record, which has stood for 50 years.

The warning came after a fast escalation. On 19 June, forecasters issued an amber alert for extreme heat. Within days, as models became clearer, they upgraded it twice—first raising the expected peak from 35°C to 38°C, then finally to Red. A Red Warning means the health and infrastructure impacts are nearly certain across the population. It's the rarest alert the Met Office issues.

On Tuesday, 23 June, Surrey recorded 34.6°C. The current June record—35.6°C—was set in Hampshire in 1976, more than 50 years ago. If the forecast holds, this week will break it.

A Summer That's Already Running Hot

This heat is not arriving out of nowhere. June 2026 has already seen 16 days above 32°C, compared with nine in the entire summer of 2025. Early in the month, some areas were running roughly 10°C warmer than they normally are for mid-June—a gap that, by climate standards, counts as genuinely extreme.

The heat is part of a larger European pattern. A heat dome has settled over mainland Europe, and the UK is sitting at its northern edge. Southern Europe has felt the worst of it. This week, the hottest air mass will shift directly over England, bringing the peak intensity north.

Schools, Hospitals, and Transport Are Struggling

By 23 June, schools, hospitals, trains, and water companies were already under strain. Hundreds of schools closed early or shut entirely, even though government guidance told them to stay open. Hospitals are dealing with more patients suffering heat-related illness while staff work in non-air-conditioned wards. Train operators slow services when temperatures exceed 36°C to prevent the track from buckling.

The core problem is simple: the UK's buildings, hospitals, and rail systems were built for a cooler climate. A sustained stretch of days above 32°C—let alone 39°C—pushes them far beyond what they were designed to handle.

The UK Health Security Agency released updated guidance on 23 June and urged residents to sign up for Heat-Health Alerts by email. The alert system has four levels, aligned with Met Office warnings. A Red Met Office warning triggers the highest alert tier, which means hospitals and public health services move into enhanced monitoring and prepare for surge capacity.

What This Tells Us About the Future

Climate analysts have been tracking a longer shift: heatwaves are not just becoming more common, but also more intense—faster than buildings and infrastructure can adapt. Sixteen days above 32°C by late June is a stark data point. Meteorologists will study this week's temperatures carefully to see whether 2026 marks a new threshold for UK summer heat.

Wednesday and Thursday will show whether the forecast holds and where the record might fall.