Ojalá el aire acondicionado funcione mañana, porque hará mucho calor.

Ojalá expresses a wish/hope about something that isn’t guaranteed. In Spanish, wishes and hopes typically require the subjunctive mood, so you get Ojalá + subjunctive:

• Ojalá funcione = I hope it works.
  If you used the indicative (funciona), it would sound wrong in standard Spanish because you’d be stating a fact rather than expressing a wish.

The gender usually follows the main noun of the phrase. Here the core noun is aire (air), which is masculine, so the whole phrase is treated as masculine:

• el aire acondicionado
  Even though acondicionado ends in -o, it’s an adjective agreeing with aire.

Mañana can mean tomorrow or morning. Context decides:

• With a future time reference and weather: mañana = tomorrow.
  If it meant “in the morning,” you’d often see something like por la mañana (in the morning).

Hará is the simple future of hacer (it will do/make), used in weather expressions meaning it will be (hot/cold/etc.).

• hará mucho calor = it will be very hot.
  You could also say va a hacer mucho calor (going to be very hot), which sounds a bit more conversational. Hace mucho calor would mean it is very hot (right now).

Literally, it’s it will make a lot of heat, but idiomatically it means it will be very hot. Spanish commonly uses hacer in weather expressions:

• Hace calor = It’s hot.
• Hace frío = It’s cold.
• Hará calor = It will be hot.

The comma is common when porque introduces a clear explanation after a complete first idea:

• Ojalá ..., porque ...
  In shorter sentences, many writers omit it, but with this structure the comma improves readability and matches common punctuation practice.

Que is optional here. Both are correct:

• Ojalá funcione...
• Ojalá que funcione...
  Including que can sound slightly more explicit or emphatic, but the meaning stays the same.

Here you need porque (one word, no accent) meaning because.
Quick distinction:

• porque = because
• por qué = why (question form)
• porqué = the reason (a noun)
• por que = rarer combination (preposition + pronoun/conjunction), not used here

Spanish uses ojalá + imperfect subjunctive for more hypothetical/unlikely wishes, and often ojalá + pluperfect subjunctive for past regrets:

• Ojalá funcionara mañana = I wish it would work tomorrow (more doubtful).
• Ojalá hubiera funcionado = I wish it had worked.