Ball lightning often enters a house through an open window, but will get in wherever it can if the windows are closed. What compels it to enter a house is unclear, but perhaps it is attracted to electricity, in a house or even in a person.
On 8 September 1981 during a thunderstorm at Te Ngaere (NZ), the witness inside a house felt the building shake during a loud thunderclap and saw a 'flow of light' come in under the door.
It had no true shape but was 3 or 4 inches long and 2 inches wide, moving along the floor like quicksilver. It was bluish-silver in colour, brighter at the edges than in the middle. Arms flowed out 'like runs of oil' among the tools laid out on the floor. Eventually the 'blob' went out again under the door.
This was not exactly ball lightning, but obviously a similar type of phenomenon.
