Households are being warned to watch out for opportunistic thieves when the clocks go forward, as insurance claims data suggests such incidents see a spike around this time of year.
Co-op Insurance, which analysed its claims data from 2018, said there was a 37% surge in opportunistic thefts - where entry was not forced - after the clocks went forward.
The insurer compared claims in the five months before the clocks going forward in 2018 with the five months afterwards to make the findings.
A third (33%) of thefts after the clocks went forward last year were categorised as opportunistic, compared with a quarter (24%) in the gloomier winter months, when burglars often force entry under cover of darkness, it found.
Friday is the most common day for thieves to strike, it added.
The clocks go forward by one hour this Sunday, March 31, marking the start of British Summer Time (BST).
Ian Kershaw, head of claims at Co-op Insurance, said: "What we're seeing during this time is a trend of home-owners relaxing their home security and opportunist thieves striking."
Co-op Insurance said opportunistic crimes can happen when windows and doors are left open as temperatures increase, or when items, such as bikes or gardening equipment, are left outside the property.
Claims data also revealed that one in 10 (11%) cases were "distraction" thefts, with examples including thieves posing as builders and engineers to gain access to properties.
The report said it is important to look out for vulnerable neighbours.
John Hayward-Cripps, chief executive officer of the Neighbourhood Watch Network, said: "Our advice is if people aren't sure who is at the door, don't open it.
"Most genuine callers will have a pre-arranged appointment.
"Also, if you see a neighbour's home where it seems a window has been left open, a back gate or a shed left unlocked for example, check on them and let them know."
Here are Co-op Insurance's home security tips:
1. Remain vigilant and keep homes secure during the lighter, summer months.
2. Keep windows and doors locked.
3. Where possible, invest in a CCTV system.
4. Check on vulnerable neighbours.
5. Do not post your location on social media platforms.
6. Set your home burglar alarm.
7. Ensure outbuildings and sheds are locked.
8. Do not leave valuable items on display.
9. Do not leave car keys within reach of a letterbox.