(Author POV)
When Renand and Nafisah were in the warm tent, they were busy chatting so they didn't notice the weather around them. Some of the monitoring guards have seen the surroundings, But they only monitor the situation of the enemy, they can't predict the weather.
The weather is getting colder they think because the heater in their tent has been slightly damaged, They also don't know from the north that a big storm has been seen. They also don't know when several weather observers have tried to tell, but the signal interference makes their cellphones completely useless.
The situation seemed quiet for a while, then the wind was strong enough to shake the tent. Nafisah and Renand already looked around each other, They thought that this was just an ordinary wind.