To be hot = very popular / fashionable: "Iceland is a really hot weekend destination at the moment."
a hot favourite = someone / something most likely to win: "Red Rum was always the hot favourite to win the Grand National
a hot tip = important or useful suggestion: "He gave me a hot tip for my interview."
a hot topic = an issue which is important: "Climate change is a hot topic at the moment."
hot off the press = very new story: "This gossip is hot off the press."
to get too hot = become too dangerous: "Things are getting too hot and the relief agencies are pulling out of the area."
a hot date = a date with someone you find very attractive: "She's got a hot date tonight!"
hot stuff = attractive: "Her new boyfriend is hot stuff."
in the hot seat = in a position of responsibility: "You make the decisions – you're in the hot seat now!"
in hot water = in trouble because you have done something wrong: "If you send that email now, you'll find yourself in hot water with the boss."
have a hot temper = to get angry easily: "He has a hot temper, so don't provoke him into an argument."
get hot under the collar = get angry about something which isn't very important: "You always seem to get hot under the collar about people's driving habits. Don't let it worry you!"
hot and bothered = feeling uncomfortable, either because it's too hot, or because you have too much to do in too little time: "She's all hot and bothered now that she's been invited to the theatre this evening."
be like a cat on a hot tin roof = restless or jumpy: "He's like a cat on a hot tin roof with all this talk about redundancies."
in hot pursuit = to follow closely: "The pickpocket ran off, with members of the public in hot pursuit."
hot on the trail = close to finding something: "The police are hot on the trail of the mastermind behind the bank robbery."
hot air = something which is not as important or true as it sounds: "What he says is just a lot of hot air – don't take it too seriously."
more (something) than you've had hot dinners = an expression to mean that you've had a lot of something: "I've had more jobs than you've had hot dinners!"
blow hot and cold = keep changing your mind about something: "I'm blowing hot and cold about moving to the countryside."