The unseasonably warm weather in Britain is expected to continue as forecasters predict temperatures could exceed Monday’s record-breaking high.

The mercury topped 20C (68F) in several parts of the country on Monday – the warmest winter day since records began. Trawsgoed in Ceredigion, west Wales, experienced the highest temperature of 20.6C, while 20.4C was recorded in Northolt, west London, and 20.1C in Gogerddan, west Wales.

The previous winter record was 19.7C in Greenwich, east London, in 1998.

Luke Miall, a Met Office meteorologist, said Tuesday could be just as warm: “We could well again see similar values. Whether it will be record-breaking again, we’re not quite sure, but I think it could be quite close.”

The warm weather contrasts with last February’s “beast from the east”, which plunged temperatures below freezing and brought heavy snowfall across the country.

Cooler temperatures expected from Wednesday would be still above average for February, Miall said. However, heavy showers were possible on Thursday with temperature struggling to get above 11C.

The Green party MP Caroline Lucas said the warm weather was a concern. “I like spending an afternoon in the sunshine as much as anyone, but it’s impossible to shake the feeling that this isn’t right. After last year’s unprecedented global heatwave and last month’s deadly temperatures in Australia, our baseline perception of what’s normal is shifting.

A man uses a newspaper as a sun hat as he basks in the afternoon sunshine in Regent’s Park, central London. Photograph: Christopher Furlong/Getty Images

“We are living through climate breakdown and, instead of taking urgent action, ministers carry on as if nothing has changed. The government must wake up to this crisis, urgently declare a climate emergency and introduce a Green New Deal to provide a green job to everyone who wants one and transform our economy to prevent climate catastrophe.”

Bob Ward, a director at the centre for climate change economics and policy at the London School of Economics, said while warmer temperatures were often welcomed they could be deadly.

“People may find it very pleasant to be in warmer temperatures but they must also remember that it’s the same trend that saw hundreds of people die last summer as a result of overheating,” he said.

“Over the past five years, we also had two record wet winters during which there was severe flooding. This is a sign of the fundamental and profound way that Britain’s climate is changing.”

He said the weather change could also have disastrous consequences for wildlife. “If we have a cold [snap again] now there is a danger it will kill a lot of wildlife that has emerged early due to the spring-like temperatures.”

Tuesday was expected to start with some light frost and fog before the temperature climbs to 20C. North-west Wales and London were forecast to be the warmest parts of the country.