UK supermarket price inflation dropped to 2.1% in the four weeks to 9 June, down from 2.4% a month earlier and the sixteenth consecutive monthly drop in the figures from Kantar.
Over a 12-week period, inflation stood at 2.3%, down from 3.1% in the April survey.
Costs were falling in nearly a third of the grocery categories tracked by the research firm, including toilet tissues, butter and milk, which compares to just 1% of items declining in May last year.
This easing inflation and frequent rainy days led to the lowest sales growth in two years, with take-home grocery sales up 1.0% in value terms in the four-week period.
"The sixth wettest spring on record hasn’t just dampened our spirits leading into summer, it’s made a mark on the grocery sector too as it seems Britons are being put off from popping to the shops," said Kantar's head of retail and consumer insight, Fraser McKevitt.
"We’re not yet reaching for those typical summertime products and are making some purchases you wouldn’t expect in June.
"Consumers bought nearly 25% fewer suncare items this month compared with last year, while prepared salads dipped by 11%. On the other hand, warming fresh soup sales jumped by almost 24%."
The drop in inflation contributed to slower market growth for supermarkets but has started to be felt by some consumers.
In a separate survey, Kantar found that 36% of households described their financial position as "comfortable" last month, the highest since November 2021, though 22% of households still said they’re "struggling", either unable to cover their expenses or just making ends meet.