Sharkado's Wikipedia entry lists it under "2010s science fiction films" hierarcy.
It was shown on SyFy TV channel.
Movie Trailers Youtube Channel listed it under Sci-Fi
Its premise is Science-Fictiony: a storm with tornadoes capable of lifting sharks into the air.
While IMDB lists it as "Horror" genre, Horror in and out of itself does not preclude being ontopic for SFF site - we have plenty of ontopic questions about works that are Horror (Dracula, Lovecraft, etc...)
I would argue that Sharknado is on-topic here, because it falls under the realm of science fiction.
(i.e. I disagree with Richard's answer which claims that the film cannot be science fiction, because the phenomenon of rains of animals has been recorded historically and is therefore established as scientific fact).
Stories playing in the present, mainly influenced by a scientific phenomenon which may be possible but has not happened so far, are generally counted as science fiction.
This includes the entire sub-genre of apocalyptic fiction. Tales about disasters such as a widespread plague, a meteorite impact, a thermonuclear war, are generally considered Science fiction.
Sharknado deals with a local apocalypse, not a global one, but I would argue that that does not preclude it from being counted as science fiction.
The important thing is, as far as I understand, Sharknado explores the consequences of a phenomenon that has a scientific explanation, but has not happened so far. (Whether the scientific explanation is sound is another matter, but that just says something about the quality of the movie, not whether it is on-topic here)
If the movie instead suggested a supernatural explanation or malevolent force behind the phenomenon, it would fit more into the fantasy genre (but still be on-topic)
No, it is not Science Fiction, but it is Speculative Fiction and thus on topic (alas).
Speculative fiction is an umbrella term encompassing the more fantastical fiction genres, specifically science fiction, fantasy, horror fiction, weird fiction, supernatural fiction, superhero fiction, utopian and dystopian fiction, apocalyptic and post-apocalyptic fiction, and alternate history in literature as well as related static, motion, and virtual arts.
I don't know the answer for sure; I haven't watched the film. That's why I started with a comment and then, after waiting and not receiving any rebuttal, went on to vote to close.
My reason for challenging it was having read a few summaries (eg Wikipedia) and not seeing anything in those summaries implying sci-fi. Eg I don't consider a "freak storm" sci-fi, unless it is caused by a mad scientist or an alien1.
I don't consider any of the reasoning in this question to make it sci-fi: eg Wikipedia might list it under sci-fi because it's got to go into one genre - but unless it has something specifically sci-fi in it I don't think we should accept it.
Richard says it is fantasy. But there is (using his definition) no magic, supernatural events, make-believe creatures or exotic fantasy worlds. He has highlighted, "and the extraordinary". But every film contains something extraordinary - otherwise it would just be a film about everyday life. "Extraordinary" is far to broad and vague to use to categorise a film as on topic for this site.
So my answer is: "Sharknado is off-topic for Sci-Fi & Fantasy". Please upvote if you agree; please downvote if you don't. May this community decide!
1 Or an mad scientist alien... or a time travelling - no, let's not go there.
Science fiction is defined as:
Fiction dealing principally with the impact of actual or imagined science on society or individuals, or more generally, literary fantasy including a scientific factor as an essential orienting component
Since the phenomenon of rains of animals (and in particular rains of fishes) has been recorded historically and is therefore established as scientific fact, the Sharknado isn't science fiction per se.
However, since a rain of sharks would be a vanishingly rare event and because the sharks we see in the film seems to possess a level of aggression well beyond that of their real-world counterparts, it's still very much on-topic for the site since it falls under the heading of fantasy, e.g.
Fantasy films are films with fantastic themes, usually involving magic, supernatural events, make-believe creatures, or exotic fantasy worlds. The genre is considered to be distinct from science fiction film and horror film, although the genres do overlap. Fantasy films often have an element of magic, myth, wonder, escapism, and the extraordinary.