Police in Bristol say they expect 'major disruption' in Bristol tomorrow as climate activist Greta Thunberg arrives.
Groups from across the country are expected to attend and officials warn normal procedures 'may not be adequate'.
The council say some roads are being closed - but can't give details yet as organisers haven't told them what they'll be doing.
The Swedish camapigner is joining the city's 'Youth Strike 4 Climate' protest - meeting in the city's College Green.
A joint statement from Mike Jackson, Bristol City Council Executive Director and Supt. Andy Bennett, Bristol Police Commander, says: "Bristol City Council and the Avon and Somerset Police are working together to manage public safety and minimise disruption to the city during the Youth Strike 4 Climate protest which will be attended by climate activist Greta Thunberg on Friday 28 February.
"From the information we know about the event, we know there will be major disruption to the city on Friday.
"We have seen a number of protests over the last year however this one will be significantly larger so we want to ensure that anyone planning to attend is prepared and able to make their own safety and safeguarding arrangements.
"Parents are responsible for their children. The council and police are not responsible for unsupervised children.
"Bristol City Council and the Avon and Somerset Police are unable to accurately predict how large this event will be however we have confirmation of people travelling from across the UK to attend.
"The event has grown so large that the usual controls, stewarding and safety measures that are routinely put in place by the teenage Youth Strike 4 Climate organisers may not be adequate, especially for primary school children and people with disabilities.
"We would therefore encourage those attending, or who are responsible for children who wish to attend, to consider their arrangements carefully and make their own informed decisions.
"The council will be closing some roads to minimise risk of harm to road users, pedestrians and protestors. The organisers have been unable to clarify full details of timings and routes, so we cannot at present give final details of road closures. Please look out for further communications.
"In terms of big crowds, there is the potential for trips, slips, falls and crushing. People can easily be separated from their friends and family. Mobile phone signals can be intermittent due to saturation on the communications masts. It is also unlikely people will be able to leave the area quickly, and access to toilets and water will be very limited. There will also be delays to public transport.
"Please do not underestimate the scale of this protest.
"We’re working to ensure Bristol is open as usual, but would urge people to allow extra time for travel and consider whether their journey is necessary."