The problem with a weather station as described is it will only give you the ambient temperature of the van as is or has been. The op was looking for a way to charge a Lifepo4 battery without damaging it through being too cold? My Lifepo4 will take a light charge at zero and discharge without any problem well below zero, so I’ve left the solar mppt charger to do it’s own thing because this time of year when temperatures are low, it will only produce a small current.As said a cheap weather station is exactly what you need, they even have max and min recall button that tels you the max and min temp over last 24 hour's just a couple of aa batterys