THE weather forecast for the next few days is sun, sun, sun - and then snow.
Experts have predicted wintry showers and frost to bring an abrupt end to a sunny spell across Wales and the rest of the UK.
A cold front is bringing gale force winds and blizzards from the Arctic with the temperatures expected to drop to minus 4 C (25F) on Monday in Snowdonia, the Brecon Beacons and parts of the Valleys.
John Hutchinson, forecaster for MeteoGroup UK, the weather division of the Press Association, said, "Generally speaking the forecast for Wales on Monday is quite cold and wintry.
"Snowdonia, the higher parts of the Valleys and Powys will get the worst of it overnight.
"During the daytime on Monday there's going to be wintry showers across the higher ground and there will be some snow around.
"By Monday evening the snow showers are likely to be in the Western areas."
At the National Botanic Garden of Wales, in Carmarthenshire, staff are getting ready to protect more sensitive flora that have flowered early due to the mild winter.
Senior horticulturalist Laura Davies said, "We'll be protecting a few plants on Sunday night that are borderline.
"We'll be putting out an extra layer of straw or covering some things up with pots if they're borderline hardy.
"But we've got thousands of daffodils in flower here and many other spring plants are hardy and we don't expect them to get damaged by a late frost."
Other forecasters said the weather represents a marked shift away from the mild winter we have just enjoyed and will be made worse by a "significant wind chill".
Senior forecaster for MeteoGroup Stephen Davenport added, "We will have biting north-westerly winds with significant wind chill to make it feel even colder.
"These north-west winds are dragging colder air from the Polar and Arctic regions. This isn't untypical of March. It's a very changeable month with the weather changing from winter to spring-summer so you are likely to get incursions of spring-like and wintry weather."
The topsy-turvy weather is likely to upset animals woken early from hibernation by the record breaking mild winter this year.
Moles, squirrels, dormice, bats and hedgehogs have been woken by the warmer temperatures and have been venturing out from their nests more often than usual.
The cold snap means food could become scarce and many may die.
Thousands of butterflies, such as red admirals, tortoiseshells, peacocks and brimstones, woken early from their big sleep may not survive the next few days.
Environmental scientist Dr Tim Sparks said, "Many of these animals need to feed every day. If there are several days where they can't access food because the ground is frozen or covered in snow that can lead to death.
"The wren is one where traditionally a prolonged cold spell can cause lots of deaths but each pair can have 10 offspring which means the population can recover quite quickly.
"The weather has encouraged them to wake early. I have seen butterflies right through the winter which is unusual and very early activity with bats and hedgehogs.
"This isn't traditional behaviour and it really depends on how severe and how long that cold period lasts. If it's three or four days then there will be severe damage to the less hardy animals and plants."
Dr Sparks, from the Centre for Ecology and Hydrology, added, "There has been early blossoming because it has been so warm almost right through winter with little frost.
"When you have temperatures as warm as they were in January and February it just encourages everything to be that bit early."
Hardier plants such as the blackthorn, the forsythia and the hawthorn which have blossomed early this year should survive the cold spell, he said.