Going to in the First Conditional

OP is unsure if "going to" can be used in the First Conditional.

"If the weather is rainy, I am going to read a book at home." The if-clause is in the first conditional, but what about the main clause?

The structure of a first conditional sentence is "if/when + present simple" followed by "will + infinitive". For example: "If it is sunny tomorrow, we will go to the beach."

In OP's sentence, the main clause uses "going to" instead of "will."

The "going-to" future refers to planned or intended actions in the future.

We can use the future with going to instead of will in the first conditional. Going to implies a more certain future than will.

• If no one comes to my birthday party, I’m going to be really unhappy.
• John is going to buy that house if he has enough money. The First Conditional is about possible events in the present or the future.
  .
  Going to in the first conditional

If it rains, I am going to read a book." is the First conditional because the "going-to future" is used to talk about a future event.

Going to in the First Conditional

OP is unsure if "going to" can be used in the First Conditional.

"If the weather is rainy, I am going to read a book at home." The if-clause is in the first conditional, but what about the main clause?

The structure of a first conditional sentence is "if/when + present simple" followed by "will + infinitive". For example: "If it is sunny tomorrow, we will go to the beach."

In OP's sentence, the main clause uses "going to" instead of "will."

The "going-to" future refers to planned or intended actions in the future.

We can use the future with going to instead of will in the first conditional. Going to implies a more certain future than will.

• If no one comes to my birthday party, I’m going to be really unhappy.
• John is going to buy that house if he has enough money..
  The First Conditional is about possible events in the present or the future.
  .
  Going to in the first conditional

If it rains, I am going to read a book." is the First conditional because the "going-to future" is used to talk about a future event.

"Going to can be used in First conditional.
OP is not sure , if 'going to' can be used in the First conditionals.

But I'm not sure which conditional the main clause is in this sentence: "If the weather is rainy, I am going to read a book at home". The if clause is first conditional, but what about the main clause?

As per Ref : Mylittlepublishing.com it is first conditional. https://www.mylittlepublishing.com/en/grammar/first-conditional-if-present-will/

The First Conditional is about possible events in the present or the future.
The main clause contain the future tense (will or « going to »).
If you come, you will see him.
If you come, you’re going to see him..

If it rains, I am going to read a book." is the First conditional because the Present continuous is used to talk about the future

Going to in the First Conditional

OP is unsure if "going to" can be used in the First Conditional.

"If the weather is rainy, I am going to read a book at home." The if-clause is in the first conditional, but what about the main clause?

The structure of a first conditional sentence is "if/when + present simple" followed by "will + infinitive". For example: "If it is sunny tomorrow, we will go to the beach."

In OP's sentence, the main clause uses "going to" instead of "will."

The "going-to" future refers to planned or intended actions in the future.

We can use the future with going to instead of will in the first conditional. Going to implies a more certain future than will.

• If no one comes to my birthday party, I’m going to be really unhappy.
• John is going to buy that house if he has enough money. The First Conditional is about possible events in the present or the future.
  .
  Going to in the first conditional

If it rains, I am going to read a book." is the First conditional because the "going-to future" is used to talk about a future event.