KINGSPORT, Tenn. -

As the mercury drops overnight and into tomorrow, local shelters are opening their doors to help keep people warm.

We checked with the Salvation Army in Kingsport and learned every time the temperature drops below 40 degrees they operate under what's called "white flag" conditions, meaning anyone who needs a warm place to sleep can stay at their shelter overnight on cots, extra beds, or sofas.

We learned on a typical "white flag" night about 11 people show up needing help keeping out of the cold.

"If it's really cold in the afternoon before check in, they can some in and warm up in our lobby a little bit, especially if it's getting [frigid] outside," said Whitney Tomberlain, the youth director with the Salvation Army in Kingsport.

We learned the Salvation Army and Haven of Rest in Bristol, as well as the Haven of Mercy in Johnson City will also be able to help people stay warm if needed.