In the capital, many among the lunchtime crowd ditched their thick winter wear and went out in suits instead. Several runners pounding the pavement in the 5 km route around the Imperial Palace were seen in T-shirts and shorts.

The Japan Meteorological Agency (JMA) attributed the warmer temperatures in the Greater Tokyo area, which saw its first snowfall of the season on New Year's Eve, to a "warm front from the south".

As at 11 a.m., the highest recorded temperatures in Chiba (east of Tokyo) was 15.2 deg C, 14.4 deg C in Maebashi (north of Tokyo), and 12.3 deg C in central Tokyo.

The mercury is expected to rise as high as 18 deg C in central Tokyo and 17 deg C in Yokohama - south of Tokyo - by Tuesday afternoon.

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The JMA warned that higher temperatures in the region could lead to avalanches in areas that typically encounter heavy snow.

Meanwhile, the JMA also warned of a rapidly-developing low pressure system and strong winter atmospheric conditions that could bring gale-force winds to northern Japan in conditions that are expected to last until Friday.

Maximum wind speeds are expected to reach 25 meters per second (m/s) in Hokkaido, 23m/s in the Tohoku region that includes Fukushima, and 22m/s in the Hokuriku region that borders the Sea of Japan/East Sea.

Snowfall of up to 50cm is expected in areas in Hokuriku, and up to 40cm in many areas in Hokkaido and Tohoku, the JMA added.

As at 2 p.m., weather warnings for snowstorms were in effect in Hokkaido and Yamagata, while blizzard warnings were in effect in six prefectures including Aomori in the north and Fukushima in the north-east.