We use «there was / were» for the past.
There was a serious car crash on one of the main roads yesterday.
Were there any letters for me while I was out?
There wasn’t any money in the purse. It was empty.
In the present perfect tense we use «there has / have been».
Look! There has been an earthquake.
This part of the country is very dangerous. There have already been a number of earthquakes this year.
For the future we use «there will be».
I don’t think there will be a lot of traffic on the roads tomorrow.
Let’s pack our suitcases today. There won’t be time tomorrow.
It versus There
Remember that when we talk about the weather, two structures are possible. We use «There… + noun» but «It… + adjective / verb».
There will be strong winds tomorrow. – We use There will be here because of the noun (winds)
It will be windy tomorrow. – We use It will be here because of the adjective (windy)
It rains a lot in autumn.
There is a lot of rain in autumn.
It was very cloudy yesterday.
There were a lot of clouds in the sky yesterday.