The early bulb flowers are starting to appear and there is a definite feeling of spring in the air, at least in the southern half of Britain.

The record for the warmest night in January was broken in several places across the South on Friday night, including 13.2C (55.8F) in London, beating the previous record of 12.7C (54.9F).The record for the highest daytime temperature on January 20 was equalled yesterday when it reached 15C (59F) at Great Malvern, Worcestershire.

At this time of year the Sun is far too weak over Britain to raise temperatures this high. Instead, the source is warm air swept up from the Canary Islands on an anticyclone. There will be further mild conditions in the South today, and temperatures may rise even higher on Wednesday.

The northern half of Britain remains in the grip of winter, with more heavy rain and the threat of flooding. As cold polar air sweeps in from Greenland, much of that rain may turn to snow over southern Scotland and the Pennines, with up to 20cm (8in) of snow forecast for today.

The outlook is likely to remain volatile this week, with Britain split between north and south. Wet and windy Atlantic depressions will battle with an anticyclone that is trying to establish itself from the south.

This wild weather is caused by a climate phenomenon known as La Niña in the Pacific Ocean. The waters have cooled and pushed the Pacific rainbelt towards the east coast of Australia, which is being battered by heavy rainfall. This also affects the jet stream, a ribbon of very strong winds a few miles high in the atmosphere, which has steered depressions in the Atlantic towards Britain.

Today

Cloudy over much of Britain, with heavy rain or snow over northern England. Low 4C, high 12C in the South

Tomorrow

Drier, brighter, but rain later. Windy at times. Heaviest rain in the North West. Cold in the North, 3-7C. In the South average 9-10C

Wednesday

Windier with rain, heavy at times mostly in the North. Unsettled until the weekend. 7-10C in the North. High of 13C in the South