"Longtemps je me suis couche de bonne heure," records Marcel Proust at the beginning of A la Recherche du Temps Perdu: "For a long time I used to go to bed early." This is something unlikely to be achieved very often by those who attempt to read the 12-volume narrative in its entirety - a growing band, it seems, following the release of Raoul Ruiz's film version of the epic.
Weatherwise, however, it is worth the effort. Proust's virtuoso rendering can transform the most mundane of meteorological occurrences into a lyrical evenement. Take, for example, his version of that most familiar happening, a "scattered shower": "A little tap upon the window-pane, as though something had struck it, followed by a plentiful, light, falling sound, as of grains of sand being sprinkled from a window overhead, gradually spreading, intensifying, acquiring a regular rhythm, becoming fluid, sonorous, musical, immeasurable, universal: it was rain."
But even stranger things can happen on a rainy windowpane. Sometimes, for example, if you watch closely, you will see the glass suddenly steam over and become opaque, clouding the pane with a window-mist that may well have gone some minutes later. Usually when transparency has returned, the rain has cleared and patches of blue sky are very much in evidence.
The sequence of events is related to a cold front passing by, which typically brings a cessation of the rain, a break in the clouds, and a sudden and very marked veer in the direction of the wind. Ahead of a front the weather outside may well be miserable, but inside the room a reasonably cosy state of equilibrium prevails; specifically, the inside temperature is high enough - or, if you prefer, the relative humidity is low enough - for no visible moisture to be evident on the inside of the window-pane; the temperature of the glass is largely determined by its contact with the air inside the room.
But if the wind veers suddenly with the passage of the front to blow directly onto the outside surface of the window-pane, the temperature of the glass drops sharply. It quickly cools the air in immediate contact with its inside surface, and within seconds the temperature of this inside air may drop below the dew point, shedding its excess moisture in the shape of little drops of water on the windowpane.
This steamy state, however, is only very temporary. Gradually the normal movement of the air inside the room wafts dryer, warmer air in the direction of the window, the obscuring water-drops are reabsorbed, and the glass became transparent once again .