Sarah,
to have this more closely match the science curriculum (Materials >Materials and Change > Heating and Cooling 1st/2nd class)
become aware of and investigate the suitability of different kinds of clothes for variations in temperature
recognise that some fabrics keep us warmer than others
design and make or assemble an outfit for someone who is going on holiday to a very warm or cold place
the children could be enabled to test the various clothing to see if it keeps them warm or cool. This can be linked to heat transfer – but heat transfer is mostly covered in 5th and 6th class, so I’d keep this simple.