A report, involving Historic England, concludes climate change is putting sites like Kew and the Royal Parks at risk.
The research covers 2,800 gardens and cemeteries and says smaller sites are most vulnerable, often because they lack the staff and money to plan ahead.
The Met Office says the UK’s on course to record its warmest-ever summer.
The average mean temperature threshold’s probably going to be met, even if the rest of August sees ‘average conditions’.
An amber heat health alert’s now covering all of England ahead of a peak forecast of 38-degrees Celsius on Thursday.
