Police were forced to turn away 60 cars at the base of Snowdon on Saturday.
Welsh authorities made the stops before 8am after issuing fines to 180 vehicles last weekend for illegal parking on nearby roads.
North Wales Police said: “Around 60 vehicles have already been turned away from Pen-y-Pass this morning with some even parking by the signage.
“Drivers said they thought we were ‘just bluffing’ when we said cars would be towed if obstructing the road.
“A recovery vehicle is already parked up there.”
Police told motorists they would not hesitate to tow away illegally parked cars to prevent a repeat of last weekend.
Llyn Tegid Car Park was already at near full capacity at 2pm.
To further prevent a build-up of traffic authorities had only allowed drop-offs at the Pen-y-Pass car park.
Leader of Gwynedd Council Councillor Dyfrig Siencyn said on Friday: “The fact is that motorists like those who parked illegally at Pen-y-pass endanger the lives of other drivers, cyclists and pedestrians and cause serious access issues for emergency service vehicles, including mountain rescue volunteers.
“We want people to be able to enjoy our stunning mountain ranges safely.
“Those who ignore the message by parking illegally on the highway on Snowdonia's mountain passes will face an on-the-spot fine or even being towed away by police.”
Police towed a further two vehicles from Snowdonia’s Llyn Ogwen lake in the afternoon.
North Wales Police tweeted: “Recovery about to tow these that are parked by #LlynOgwen.
“Although at the end of the coned area they're causing other vehicles to head into opposing lane into a blind right-hand bend.
“Pedestrians walking into the road due to the blocked pavement. Inconsiderate.”
Snowdonia National Park officially reopened on 6 July after closing at the start of the lockdown in March.