First Conditional
Is formed if + simple present + simple future. It is used when a real or potential situation is: If it rains today, I'll stay at home. Here are some examples translated.

If clause	Main clause
If + Present tense	will / can / may / must + verb
If it rains today,	I'll stay at home

• If it rains today, I'll stay at home.
  Si llueve hoy, me quedaré en casa.
• If he is busy now, I will come back tomorrow.
  Si está ocupado ahora, regresaré mañana.
• If I have time, I'll visit my parents this afternoon.
  Si tengo tiempo, visitaré a mis padres esta tarde.
• If it is warm tomorrow, we'll go to the beach.
  Si está caluroso mañana, iremos a la playa.
• If it is cold, you must wear warm clothes.
  Si está frío, debes usar ropa abrigada.