Why are my young chickens dying?

[Trinitypixie]

I have been raising chickes for 4 yrs now and I have never had this happen before. I have a mess of 3 mo old chickens in a mobile tractor. This is where I start all my chicks once old enough to be off heat.
3 times now I have gone out day after a major storm to find a dead chicken. I am so confused. One was up in the coop the other 2 were dead on the ground. We have big storms every year why are they dying now?

 

[nuthatched]

Could they have gotten wet and chilled?

 

[NatJ]

I have been raising chickes for 4 yrs now and I have never had this happen before. I have a mess of 3 mo old chickens in a mobile tractor. This is where I start all my chicks once old enough to be off heat.
3 times now I have gone out day after a major storm to find a dead chicken. I am so confused. One was up in the coop the other 2 were dead on the ground. We have big storms every year why are they dying now?

Could they be scared of the weather, crowd and pile in a corner, and smother one at the bottom? Although I might expect to find several dead chickens if that happened, rather than exactly one each time.