I think you might be, sorry.
I (US) usually say and hear "On the weekend". Most UK or Commonwealth folks I've known say "At the weekend".
But I don't think I've ever heard anyone (whose native language is English, anyway) say "In the weekend".
And, because of that I'm now blatantly curious (pardon me) - Where are you from?
I am from New Zealand, but one of my parents is from the US. I had a lot of exposure to non native speakers as a child, and traveled quite a bit, so those might have affected what sounds natural to me. But 'in' sounds to me like 'during' or 'within' so I thought it was ok.
A NZ Redditor posted about this too: https://www.reddit.com/r/grammar/comments/2lwpoh/in_vs_at_the_weekend/
BTW language does change if enough people say it a certain way (if that way makes some grammatical sense) so if we just keep on saying it, it will start sounding normal and become accepted :P
I would guess this phrase is very regional, and almost any preposition is correct in some corner of the English-speaking world. Me as a midwestern American would say "during" or "for", or simply skip the preposition altogether ("what are you doing this weekend?"), I would never use "in" or "on" or "at". But living abroad, I've heard all those prepositions, albeit from non-native speakers.
Came to the comments to say this. It seems to be missing somewhere else (can't remember the question but it's supposed to start with "В москве" but you the audio doesn't seem to have the В) as well.
But I wonder if here it's just slurred into the the beginning в of выходные.
But that brings up a question - why is it "В выходные" (or "В среду" or "В Понедельник") but then you have "Во вторник"? At first I thought it was the similar letter sound and the Во was to set it apart. However given this question, that doesn't appear to be the case.
The singular means "day off", but выходные is plural, so it means "days off". (I think - it's really hard to look up). According to Katzner's Russian-English dictionary, the adjective выходной means "1. serving an an exit 2. worn on social occasions (as a party dress)" and the noun/adjective выходной means "day off".
The plural noun выходные declines using the adjectival endings.
Acc. Inan. -ые
Acc. Anim. -ых
On all the prepositions I've seen which have added "o" (like "co"), it's because the next word begins with a consonant cluster, such вр- вс- мн- св- сл- (and perhaps more). There are probably some consonant clusters at the beginnings of words used with в that require the use of во, but I haven't seen any that I recall. Obviously, вы- is not a consonant cluster that requires that you use в instead of of во.
When I encounter consonants with "o" added, I write down the following consonant cluster in a list I keep on my computer, in a file stored on a cloud drive.
Why is выходны́е in the accusative? Wouldn't this translate to "to the weekend"? Why is it not выходны́х?
....on Wednesday, on Thursday, on Friday, on the weekend. What are you doing on Friday? What are you doing on the weekend? This weekend I'm going to the beach. Next weekend I'm going to visit my grandparents. Last weekend I had to work, but on most weekends I like to relax. I work hard during the week but weekends I like to relax"