By Sarah Mukherjee
Environment correspondent, BBC News
In some parts of the UK, flowers are already out
It's a truly, breathtakingly lovely day.
The early winter sun hangs low and pale gold behind the hazlewood trees, which are themselves frost-etched into a sky of pale, cloudless blue.
We are at the Nuttery, a patch of land managed by the Woodland Trust, near Daventry in Northamptonshire, and researchers from the Trust are showing me the signs that, despite the toe-numbing weather, spring is coming earlier.
"There are catkins out all around, and, although we're in the Midlands, the daffodils are almost in bloom," says Kate Lewthwaite, one of the Trust's researchers.
"Wildlife is repsponding to our warmer springs, which are happening because of climate change. It's happening incredibly quickly, and some of them don't have the resources to adapt."
Across the country, 50,000 researchers, part of the Trust's "Nature's Calendar" project, have reported sightings of natural events that should be happening far later in the year. Kate says there have been 100 sightings of frogspawn, and even four of tadpoles.
Red admiral butterflies are on the wing, along with bumblebees and wasps. And birds are beginning to nest. All of which, Ms Lewthwaite says, is "startling".
The problem is, researchers say, that if some species start to emerge from winter dormancy earlier than others, the complex web of natural dependency will start to break down.
If frogspawn gets frozen, it will die
Birds will be raising chicks before there are enough insects to feed them, and flowers will be in bloom before the right sort of bug is around to help with pollination.
As spring springs around us in parts of the Nuttery, leaves crack with frost beneath our feet. And this is another problem - all this early-emerging nature is very vulnerable to cold snaps.
"Frogs only spawn once a year - and if frogspawn gets frozen, it dies" says Steve Marsh, also from the Trust.
Researchers admit there's not a lot that can be done - no amount of government money can change how species react to the weather.
But they are asking for as many volunteers as possible for their Nature's calendar project, so scientists can analyse with greater accuracy just how quickly how British wildlife is changing.