Answer:
If it were warmer outside, Emily would go swimming.
Step-by-step explanation:
Were is the present subjunctive third person singular form of the verb to be. Although the subjunctive mood is not used as much in modern English as it was in the past, examples can still be found where it is utilized.
The subjunctive mood is used to express wishes or desires that do not reflect the current state of things and instead transmit an alternative possibility or condition.