explain the events which took place immediately after otis family entered canterville chase.do you think there took place something unusual?

As the Otis family entered the avenue of Canterville Chase, the sky became suddenly overcast with clouds, a curious stillness seemed to hold the atmosphere and a great flight of rooks passed silently over their heads. Big drops of rain began to fall before they reached the house. Mrs Umney, the housekeeper, was standing on the steps to receive them. She was an old woman, neatly dressed in black silk with a white cap and apron. The sudden changes in the weather seemed to indicate that there could be a possibility of some inexplicable supernatural phenomena waiting to happen. There was a promise of mystery and menace lurking in the atmosphere that is precipitated in the way in which the weather turns.