New York City cyclists may want to think twice before heading out without bike locks this summer — especially after sunset.

Bike thefts around the city have increased by nearly 120% in the past six months, according to NYPD data from 2021-2026 analyzed by rental company Holland Bikes. Nearly a third of the incidents took place in the warm summer months of July-September, with August alone accounting for more than 10% of annual bike thefts.

This year’s thefts have concentrated between the hours of 8 and 9 p.m. The data also shows that Manhattan has had more bike thefts than any other borough, with 748 reports so far this year compared to 497 in Brooklyn — the next highest.

It’s not all bad news for cyclists in the city: The total number of bike thefts is still down compared to last year. All boroughs are seeing meaningful declines, except for Queens, where thefts are up about 7%. But summer’s increase in incidents is closing the citywide gap — 440 bikes were stolen this June alone, compared with 457 last June.

The NYPD says it’s aware of the increase, and is working to combat the thefts by encouraging riders to get their bikes registered with the department — which involves engraving a serial number on each bike in a discreet location and sticking a decal to it that says it has been registered with the NYPD. If a bike thief removes the decal, the word “void” is left behind, which alerts police that the bicycle has been stolen. Officers are then able to track down the owner through the engraved serial number.

Holland Bikes managing director Eric van der Zanden called the overall declines “encouraging,” but is also urging riders to take extra precautions.

He offered the following tips for avoiding bike thefts:

“When locking up your bike, opt for a high-rated U-lock and place this through the bike frame as well as one of the wheels before securing it to an immovable rack. Aim for locations in clear view of CCTV that are well-lit and have high foot traffic if possible.”“Avoid leaving your bike locked in the same public spot overnight during peak theft hours by changing the location you park it, as this makes it more difficult for thieves to know when it will be left unattended.”“Riders should consider signing up to the NYPD’s Bicycle Registration Program, which involves engraving a serial number onto your bike to show it is registered with the police, as this allows them to contact you more easily should it be stolen and recovered.”

Two-thirds of bike thefts this year took place on city streets,while just 17% took place at owners’ homes, according to the data. Grand larceny cases, which typically involve higher-value bikes and e-bikes, account for 53% of all New York bike thefts, while petit larceny cases — bikes valued at less than $1,000 — make up the other 47%.