Here is another idea:

Rather than create a new chart each time, just change the data source of the chart that already exists on the sheet. In the below example the chart I was working with was named "Chart 4". This way you can format the chart and the changes will stick.
Sub Create_Dynamic_Chart2()
    Dim sht As Worksheet
    Dim chrt As ChartObject
    Dim data_rng As Range
    Dim dRange As Range
    
    Set sht = ActiveSheet
    Set dRange = Range("A2") ' dropdown
    
    Select Case dRange.Value
        Case "Charelville"
            Set data_rng = Range("tblCharlevilleTemps")
        Case "Dalby"
            Set data_rng = Range("tblDalbyTemps")
        Case "Toowoomba"
            Set data_rng = Range("tblToowoombaTemps")
        Case "Warwick"
            Set data_rng = Range("tblWarwickTemps")
    End Select
    
    Set chrt = sht.ChartObjects("Chart 4")
    With chrt.Chart
        .SetSourceData data_rng
        .ChartTitle.Text = Range("A2").Value & " Min & Max Temps"
    End With
End Sub
In answer to your question above:
Lower the labels on the Y axis: Right click on the date axis, select 'Format Axis', in the 'Labels' part, change the dropdown to the 'Low' option.

If you format the chart with the above and also use the code above, the changes on the chart will stick rather than resetting each time you add a new chart.