This is what I found online.
No. It is not safe to bring a 4-month-old into a whirl pool or jacuzzi-type bath that has a high temperature. Most public spas or jacuzzis will have a sign posted stating that infants should not be allowed in it. The reason for this is that most of these types of spas have a water temperature of over 100 degrees. Young children, in particular, have a much more difficult time regulating their body temperature. When exposed to these high water temperatures, their body temperature can rise significantly and quickly, causing difficulty with a number of metabolic problems.