The baby is thought to be the only child of a young couple who live in the Tipperary town area.
She had been taken by ambulance to a local gaelic football field at around 1.45pm then taken by air ambulance to the University Hospital in Limerick.
"Lecture Circuit" included guest appearances by screenwriter Dan Goor, comedian Rob Huebel and actress Rashida Jones, who reprises her role of Karen, a regular character from the third season.
The seven-month-old girl was in the car in Country Tipperary, the Republic of Ireland as temperatures soared to 23C today.
Her dad was about to drop her off at a creche at 8am before he got distracted and forgot her, it is reported.
Cops are investigating the death, although it is being treated as a tragic accident.
"Lecture Circuit" is a two-part episode of the American comedy television series The Office.
When Michael goes to Holly's desk he cuts a sleeve off her sweater, and notices a document on her computer called "Dear Michael", which he copies onto his flash drive.
Later, at a diner, Michael tells Pam about the letter, but she insists reading it would be violating Holly's trust.
Michael (Steve Carell) is asked to visit the Dunder Mifflin branches to lecture about his success in Scranton.
He and Pam (Jenna Fischer), who is coming along as his assistant and driver, plan to visit every branch except Nashua because Michael is not ready to face his ex-girlfriend Holly, who works there.
The heartbroken child's family raced to be at her side in hospital but she passed away shortly after 5pm.
They are being comforted by family, friends and neighbours.
They first visit the Utica branch, where former Scranton employee Karen (Rashida Jones) is now regional manager.