The mature fir tree was struck by a “significant” bolt of lightning at around 9am this morning (Saturday).
A tree specialist from Worthing Borough Council visited the scene at Burford Close, but deemed that the tree could not be saved.
It is in the process of being cut down.
Roy Barraclough, district commander at Worthing Fire Station said: “This is a lovely mature tree and probably one of the biggest trees in Worthing.
“It was a severe strike and it has gone right through the middle of it meaning that it cannot be saved as it is already dead.
“About half a dozen houses have lost power and some have lost their telephone lines.
“We have had the Red Cross out to talk to those affected and to make sure that they are okay.
“There is no other option but to cut the tree down but it will make quite a difference to the skyline as at 25 metres high it is quite a distinguishing feature of this area of the town.”