you can access to json Object values with thier keys, for example:
response.body.list[0].main.temp_min
You should use 'Dot Notation' to access the required object property. Refer to the MDN Docs or a resource like W3 for more information on how to use this.
In your case, you could declare a variable equal to the property you wish to access:
minTemp = response.body.list[0].main.temp_min