You would just say 'It's 30 degrees'. Or, if it's clear that the conversation is about the temperature, you could simply say 'It's 30'. For example, you'd say "It's a bit cooler today, isn't it? It must've been about thirty yesterday." We wouldn't use 'plus' at all, because it generally goes without saying that you're talking in positive figures. By the way, it also goes without saying that you're talking in degrees Celsius. Nobody uses Fahrenheit apart from the USA, so only Americans feel the need to specify 'Celsius'. Everyone else assumes that temperature is measured in Celsius,so there's generally no need to add this.

Hello Victoria. If talking about something as common as the weather, we would usually omit the "+" and just say: "30 degrees [Celsius/centigrade].” If the temperature were -30°C, we would be sure to say: "negative 30 degrees [Celsius/centigrade],” or "30 degrees below zero." If speaking about something less common (or in a scientific context) we would say "positive 30 degrees [Celsius/centigrade]" Also, in the United States, we predominately use the Fahrenheit scale. Typically, the only time we would use Celsius is when talking in a scientific context.

For that temperature (+30C), I'd only say: "It's 30" or "It's 30 degrees". Nothing else. I would never use plus (or minus) unless the temperature was much closer to 0 and you wanted to be sure to be understood (that it was above or below zero). For instance if it were +2C, I'd say one of the following: "It's 2 above", "It's 2 degrees above", "It's plus 2", "It's plus 2 degrees". But even here sometimes you just say "It's 2" or "It's 2 degrees".

Hello Victoria. If talking about something as common as the weather, we would usually omit the "+" and just say: "30 degrees [Celsius/centigrade].” If the temperature were -30°C, we would be sure to say: "negative 30 degrees [Celsius/centigrade],” or "30 degrees below zero." If speaking about something less common (or in a scientific context) we would say "positive 30 degrees [Celsius/centigrade]" Also, in the United States, we predominately use the Fahrenheit scale. Typically, the only time we would use Celsius is when talking in a scientific context.