London gets its first heat plan as 40C nears. Few recent summers reached 35C.

What happened

The Mayor launched Heat Ready London, the capital’s first heat plan, as forecasters predicted temperatures up to 40C and the second Red Heat-Health Alert on record took effect.

Forecasters expected up to 40C when City Hall launched its plan. Record June heat had set off only the second Red Heat-Health Alert since the current warning system began. The plan, called Heat Ready London and launched on 25 June, covers cooling spaces and public drinking water, and work to protect high-risk homes from overheating.

It also covers greener streets, safer swimming in rivers and lakes, and heat planning for the NHS and the transport network. London Councils, Transport for London and the London Fire Brigade are named as the partners who will deliver it.

The launch came at the end of a hard week. On 22 June Sadiq Khan issued a high air pollution alert on advice from forecasters at Imperial College London. They warned that strong sunshine would turn polluting gases in the air into ground-level ozone. Londoners were asked not to leave engines running or burn garden waste.

Khan said rising temperatures were already a growing reality for Londoners, and called the plan a call to action for partners to protect the most vulnerable. The first test comes soon: whether July and early August bring the 35C-plus heat the plan was written for.

Sources: London City Hall (2)

The Pattern

London passed 35C in three of the ten summers before this one. We looked at when its biggest heat spikes came. They are short and sharp, and they usually land in late July or August. A hot June has not meant the peak of the summer was over.

The Read

History points both ways. This year already looks like a hot one. A June with only the second Red alert on record and forecasts near 40C suggests the kind of weather that brings London’s biggest peaks, and the warming climate adds to that. Every summer in the past ten years that passed 35C was already running hot. The last three records, in 2022, 2020 and 2019, all came between 19 July and 1 August, inside this question’s window.

The case against is the record itself. In seven of the last ten summers London never reached 35C. Heat spikes are short, so two hot days that peak at 34.5C would still count as a no. British summers also break. The record week of 2019 gave way to a wet August, and a hot June often turns into an unsettled July. The market at 61% leaves room for June being the peak of this summer.