Dyfed-Powys Police is asking people in rural communities, particularly farmers and landowners, to be on the alert over the next few months for warning signs of any illegal gatherings.
Police say social networking has made it easier for organisers to spread the word of events and numbers attending could quickly grow.
A recent large gathering in Ceredigion caused local disruption with people traveling from far afield to attend an unlicensed event.
Gatherings – such as illegal raves – can be difficult to stop due to the numbers of people involved and the safety aspects surrounding breaking up such an event.
Chief Superintendent Aled Davies said: “There is little doubt that these type of events are very well planned, organised and that local knowledge is important in drawing down the main group to a particular ‘vulnerable’ field, or area of land which has been targeted previously as a suitable venue.
"Farmers, landowners and local communities are encouraged to report any suspicious activity immediately to the Police; this may be an unusual numbers of vehicles, especially camper vans, vans or trucks in the locality, illegal trespassers who may be doing a ‘recce’ of sites in advance of the event.
“I can assure local communities that Police will take the appropriate action to work with our partners to deter illegal gatherings and deal robustly with any criminal offences discovered or disclosed.”
Members of the public are also urged to be vigilant of persons who approach landowners enquiring for land, in the guise of hiring for seemingly acceptable activities such as gymkhanas and fetes.
Contact police on 101 with reports of any suspicious activity.