[2] Crossing France, Belgium, Luxembourg and Germany between 25 December and 27 December 1999, Cyclone Lothar's average winds reached up to 115 km/h inland (Orly), but with gusts exceeding 150 km/h, almost equivalent to a Category 2 hurricane,[3][a] resulting in 110 deaths (including 88 in France alone)[6] and more than €15 billion in damage, becoming the costliest European windstorm ever recorded.

[3] It was the second of a series of devastating European windstorms which made landfall in December 1999,[7][8] occurring around three weeks after Cyclone Anatol, which caused severe damage in Denmark and nearby parts of Sweden and Germany.

[9] Starting on December 20, 1999, the Iceland depression strengthened and created a strong temperature contrast along a polar front across the Atlantic.

A very deep and sizable depression moved across Britain on the night of 24–25 December (analysed to have possibly reached a low of 938 mb between Scotland and Norway),[10] this set up a large area of westerly flow into Europe which brought Lothar.

This highly unstable situation inevitably meant low predictability, and saw an unusually straight and strong jet stream (similar circumstances were also noted the day before the arrival of the Great Storm of 1987).

This storm, called Martin, followed a path 200 km south of Lothar and reached its recorded minimum pressure of 964 hPa.

[8] The strong jet stream that was the chief cause of the instability was well predicted by the European Centre for Medium-Range Weather Forecasts 9 days earlier.

Consequently, the power and extent of the storm was only recognized in the early morning of 26 December, which resulted in shorter warning times in Switzerland.

The identification of this secondary area and its frontal systems contrasts with the analysis of the German Weather Service which suggested that solely a 'trough line' crossed Germany.

In less than half a day the storm tore across France, Belgium and Germany, only finally beginning to weaken as it crossed Poland.

The Palace of Versailles and its monumental park were considerably damaged (over 10,000 trees were lost within two hours, including valuable specimens planted by Napoleon and Marie Antoinette).