Police are threatening to tow away cars parked illegally outside a popular Lake District National Trust site.
The hot weather had caused a "significant increase" in visitors to Fell Foot Park near the Windermere shore, Cumbria Police said.
Officers estimated 150 vehicles had been left blocking double white lines on the A592 last weekend.
Insp Paul Latham said the force had "serious concerns over the manner of parking".
"They are not only committing a road traffic offence but are causing significant obstruction to other road users," he said.
Those parking dangerously are being warned they also face a £100 fine and three points on their licence.
Parking regulations prohibit parking on a road marked with double white lines, except for dropping off passengers or loading.