Seven cars were torched in Hightown on Saturday with six others hit in June.
Kevin Jones, from North Wales fire service, said: "This is a serious issue, not only is it extremely upsetting for the owners of the vehicles damaged, but it could potentially be life threatening."
North Wales Police is investigating.
The latest incidents happened on Waterloo Close and surrounding streets within an hour on Saturday morning.
Det Insp Jonathan Salisbury-Jones said: "I am appealing to anyone in the area at the time who saw any suspicious persons or activity, or who knows anything about these fires or witnesses any anti-social behaviour to contact police immediately.
"These incidents not only put the community at risk but also waste the resources of the emergency services which could be put to use elsewhere."
Anyone with information has been asked to contact police on 101 or via Crimestoppers on 0800 555 111.
An investigation is continuing following a second spate of car arson attacks which have wrecked 13 vehicles in one Wrexham community.