Bonjour William,
This is a very interesting question!
- if you're predicting for something to happen -> Prévoir que + Futur Simple (Indicatif)
Je prévois qu'il fera beau = I predict it will be sunny
-> it's a prediction of something you're sure about
- If you are planning for/expecting something to happen -> Prévoir que + Mode Subjonctif
Je prévois qu'il fasse une bêtise = I expect him to do something silly
-> you're anticipating what might happen ; leaving a doubt.
So, depending on the meaning of "prévoir", you might use Le Futur Simple (L'Indicatif) or Le Mode Subjonctif.
I hope this is helpful.
Bonne journée !
