Concept
Understand that to measure the wind and temperature through the very low atmosphere, say up to 5,000 ft but at least 3,000, then a small drone makes sense which could either be slung in the boot in the landing field or in the ruck sack before climbing up. A balloon would need a source of helium, a lot of string, measuring device and tx with battery. Small cheap drones with tx already exist which only need a couple of sensors.