今日はお祭りですって英語でなんて言うの？

Well, if you wish to inform someone that there is a festival today, it's probably best to, at least, name the festival. Generally, the name itself will explain the type of festival it is, otherwise you may need to explain.

"There is a _______ festival today that you can check out!" I added a blank space you can fill in (beer festival, music festival, lantern festival, etc.). A festival is a broad term so adding a descriptive word can help. "You can check out." is a handy term to know, it means that you can go to and see. "There is a ______ festival today at _(place)_ if you're interested!" Once again I added a blank space :). I added the second blank to add a place. "There is a folk music festival today at the public garden, if you're interested." This is giving a tourist a lot of information to help them make a decision. You can ask "if you're interested." is just adding this to the end to ask someone if it would be something they'd like :)

When there is an event in your city that is not normally there, you can use the phrase "in town" to note that. After that, you can explain for how long the festival or event will be in your town. This is based on American English but all English speakers should understand what you want to say. I hope this helps :)

"We have a .... festival today, Would you like to come?" - You would add the name of the festival so it gives the person you are asking a bit more information into what the festival is about. Example - "We have a Winter festival today, Would you like to come?.

A festival is a celebration, so it's easy for an English speaker to understand if the word, "celebration" is used, especially together with the word, "public." Another way to say it is simply, "festival," and the person understands that anyone is free to attend by the phrase, "in the city," meaning if you're visiting that day, you can also be present to enjoy the festivities.

If you want to explain to someone there is a festival on today then you can say 'There is a festival today' or 'We have a festival on today' if you want to explain more then you can tell the person what festival it is then they would know

To add importance to the event use of adjectives like famous or grand helps the listener to understand why you are telling them this information, and will give them an excitement for the prospect of attending.

The simplest way to say the festival/event is that day is, "there's (there is) a festival today." This is the most commonly heard in conversation. Another way to say that there is an upcoming event that day is by saying, "there's a festival happening today!" A lot of times when describing events, it's common to hear someone say there is something happening. Another way you can let someone know about an event is by asking, "did you know there's a festival today?" This is a good way to start a conversation about that topic. The person will either answer yes or no, and then you can discuss more about it.

When trying to tell someone that there is a festival happening in your town/city, one may say something along the lines of "There is a festival happening here today." or "Today there is a big festival going on.". All of the above are various and simple ways of telling someone that there is a festival going on at the time.