The calendar may say April, but the atmosphere is saying February across much of Europe and northern Africa. A potent cold blast, accompanied in some spots by a rare late-season snowfall, will surge south to kick off the workweek, bringing a sudden seasonal reversal to some places that just observed their warmest March weather recorded.

Last week, the Netherlands, France, Belgium and Luxembourg established record temperatures for the month of March, while stations across broader Europe and even into Asia smashed record readings for the date. In Paris, the mercury soared to 78 degrees on March 31, its highest temperature on record for the month, according to AccuWeather.

High temperatures some 20 degrees or more above average will be replaced by a sudden chill, courtesy of an active jet stream pattern that favors hefty shifts.

Some computer models even indicate the potential for a dash of snow in Venice and along the shores of the Mediterranean, with snow also favored in Turkey and over the Black Sea. Snow was already falling in Germany on Monday.

The leading edge of the cold air was crashing south across the northern tier of Europe on Monday, having already plowed through the United Kingdom with overcast skies and a thick, dense low cloud cover. By midnight, most of Europe will be on the chilly side of the boundary, which will collapse into the Mediterranean on Tuesday and pivot east on Wednesday.

A secondary cold front could try to sneak into northwest Europe and the United Kingdom on Wednesday in the wake of a trailing storm system, potentially bringing additional snow chances and reinforcing the winterlike pattern.

The cold should finally begin to relent by the upcoming weekend.

The U.K. Met Office has much of Scotland, Wales and Northern Ireland included in yellow warnings for snow, wind and ice.

“Some roads and railways [are] likely to be affected with longer journey times by road, bus and train services,” the Met Office wrote. They warned of “frequent heavy snow showers” that could in particular affect northern regions.

With just enough moisture carried by frosty northwesterly winds, a few snow showers or flurries could even pinwheel down southern Europe in the coming days, affecting eastern France and Germany on Tuesday, much of central and southern Europe to the Mediterranean Coast into Wednesday, and even the Balkan Peninsula late Wednesday or Thursday.

In London, where the front had already swung through early Monday, the high temperature wasn’t expected to get above 45 degrees — 10 degrees below average, and more than 20 degrees shy of the 67-degree high observed exactly one year ago. Overnight lows Monday night could fall below freezing.

Glasgow, Scotland, was expecting an inch or so of snow by late Monday, with temperatures struggling to climb much above 40. That’s not too cold in comparison with the early April average of 50, but a chance of snow showers will linger through the midweek. On Saturday, the temperature hit 60 degrees in Glasgow.

Dublin could start the day with temperatures in the lower 30s and snow showers Tuesday. The city was in the lower 60s a week ago.

By Wednesday morning, most of Europe will drop below freezing, with lower 20s possible along the Spain-France border and the higher elevations in northern Slovakia and southern Poland. Elsewhere, upper 20s to near 30 will be common from northern Spain and the Iberian Peninsula east to the Black Sea and north toward Scandinavia.

The Italian Meteorological Service has hoisted a yellow warning for wind when the front comes through early Wednesday. The morning low in Milan could sit just above freezing. A few flurries are possible in areas to the east, with more appreciable accumulations east of the Adriatic Sea. There’s an outside chance that a few spots could pick up a half foot of snow in the high elevations of western Croatia and Bosnia.

Driving the exceptional cold is a pair of weather systems working in tandem to induce prolonged northwesterly winds. Clockwise winds around a strong high pressure system dropping south from near Iceland will work together with a potent low over northern Norway and Sweden to funnel Arctic air southeast all the way to the northern edge of Africa.

Meanwhile, an extra amplified, or wavy, jet stream is allowing for more dramatic temperatures swings and departures from average; last week, Europe found itself beneath a ridge, or northward meandering of the jet, which permitted mild air from the south to ride north and overspread the region. Now nestled within a pronounced jet stream dip, the opposite can be expected.

It’s commensurate with what’s to be expected in the overarching weather pattern, which is primed to allow occasional lobes of the low-level polar vortex to pinch off and bring errant, stubbornly cold air to regions typically under the auspices of spring by now.

And while the cold air outbreak is significant, its magnitude does not match that of the climate change-intensified warming that affected Europe last week, or the widespread positive temperature anomalies that dominated the region during much of January and again in late February. Earth’s temperatures continue to be skewed hot.