We use the idea of "cold" in many idioms, to refer to weather, to people, and to relationships. Here are some of the more common idioms and phrases.
ice cold / freezing cold / stone cold = very cold: "This tea is stone cold!"
a cold snap / a cold spell = cold weather: "We're in for a cold snap this weekend."
cold-hearted = not be a warm person: "She is so cold-hearted, ignoring her boyfriend like that!"
cold-blooded killer / kill someone in cold blood = have no mercy for your victim: "He was killed in cold blood."
cold fish = a "cold" person: "The new manager is a bit of a cold fish. I don't know what to make of him."
get cold feet = when you suddenly don't feel brave enough for something: "We wanted to go on holiday to Egypt, then my husband got cold feet about flying."
blow hot and cold = not be able to decide something: "I don't know about moving house. I'm blowing hot and cold about it."
in the cold light of day = when you can think clearly about something: "In the cold light of day, the ghost stories didn't seem so scary."
cold facts = plain facts: "Just give me the cold facts!"
leave someone cold = not be interested in something / someone: "I'm afraid that watching football on TV just leaves me cold."
throw cold water on something = destroy other people's enthusiasm about something: "We thought we had some really good ideas, but then she threw cold water on them."
leave someone out in the cold = not include someone: "While the others were playing cards, she was left out in the cold."
come in from the cold = be accepted into a group: "He's finally come in from the cold."
give someone the cold shoulder = ignore someone: "After the party,he was given the cold shoulder."
Cold War = the state of unfriendliness between the USA and the USSR after World War II: "We're studying the Cold War in history".
be out cold = be unconscious: "After a bottle of whisky he was out cold."
go cold turkey = to go through withdrawal symptoms from drugs: "The only way to get off drugs is by going cold turkey."
cold call = call someone you don't know to sell them something: "Cold-calling isn't always an effective sales technique."
cold comfort = a small piece of good news which doesn't make much difference to a bad situation: "Sales reductions of 50% are cold comfort if you don't have any money to go shopping!"
get / catch a cold = become ill with a cold: "I caught a cold last week."