We often use the weather to talk idiomatically about negative feelings or states. Because negativity is sometimes a difficult subject, we like to use the weather as a metaphor.

To be under a cloud is to be associated with doing something wrong or censored by someone in authority. ‘Peter left the office under a bit of a cloud yesterday, after that argument with the chief executive officer.’

To be hazy about something is to be unclear: ‘Can you clarify these figures for me, as I'm a bit hazy about what they actually mean?’ Or, ‘I'm a bit hazy about the meeting with human resources next week, could you fill me in?’ Here the speaker is asking to be ‘filled-in’, meaning to be informed about the meeting.

Gloomy is a weather adjective, used to describe a negative state of mind: ‘Are you OK? You look a bit down in the dumps?’ ‘Yes, I'm feeling a bit gloomy about the meeting tomorrow.’ Interestingly, ‘down in the dumps’ also means not very happy. We can talk of gloomy weather forecasts and gloomy financial outlooks. ‘The weather forecast is gloomy for the next couple of days, looks like a typhoon is on the horizon.’ To be ‘on the horizon’ means to be near and almost going to happen. ‘These figures don't look too good for September and the forecast looks quite gloomy for the rest of the year.’

Being ‘under the weather’ is to feel ill or depressed. We use ‘under the weather’, instead of being more direct, if we want to avoid going into too much detail about how we are feeling. ‘I'm feeling a bit under the weather today. I think I'll cancel my afternoon meetings.’ Or, ‘You are looking under the weather this morning, are you OK?’ We also use weather to talk about good things and things we hope to do. ‘Why don't we go on holiday? Let's throw caution to the wind and go somewhere really exciting.’ Here, throwing caution to the wind means not caring too much about the consequences of our actions and doing something adventurous.