Using the Present Tense for Future Events
In everyday European Portuguese, the present indicative is very commonly used to express future events when a time adverb or context makes the future meaning clear.
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European Portuguese Grammar Guide
When a time expression (amanhã, na semana que vem, às três horas) makes the future meaning clear, EP speakers routinely use the present indicative instead of the formal future tense.
Amanhã vou ao banco.
Tomorrow I am going to the bank.
Na semana que vem, começo o novo trabalho.
Next week I start the new job.
O avião parte às seis da manhã.
The plane leaves at six in the morning.
The simple future tense (falarei) is reserved for formal registers or when no time expression is present. For daily plans use the present or ir + infinitive.
The ir + infinitive construction (vou falar) is also widely used in EP for near-future events and is always safe.
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No domingo, fazemos um piquenique no parque se estiver bom tempo.
On Sunday we are having a picnic in the park if the weather is good.