Yes, it sometimes rains worms—welcome to the rainforest’s most bizarre season.
When it comes to Costa Rica’s rainy season, most people imagine lush green jungles, rushing waterfalls, and dramatic afternoon thunderstorms. But those who’ve spent enough time in the more remote corners of this biodiverse wonderland know there’s more to it than that. Every so often, you’ll hear a strange story—about frogs migrating in great chorus, puddles full of fish where there should be none… and yes, even worms falling from the sky.
It sounds like something from a children’s book or an apocalyptic sci-fi flick, but worm rain is a phenomenon that both scientists and villagers have tried to make sense of. In this tropical realm where the normal rules of nature feel a bit more elastic, the rainy season reveals its quirkiest cards.
Does it actually rain worms in Costa Rica?
Yes—and though rare, it’s not just a story to scare tourists. Worm rain has been reported across the world, and Costa Rica is no exception.
Several residents in rural zones like Tilarán, Los Chiles, and even parts of the Central Valley have told of waking up after a night of hard rain to find their patios, rooftops, or cars littered with live earthworms. Some even describe hearing the soft, odd patter of the worms landing on tin roofs during the night. They’re often discovered wriggling about in puddles or balled up in gutters—far from any flowerbed or garden.
Though it’s easy to dismiss such tales as exaggeration, similar reports have been recorded in other parts of the world, including Norway, Louisiana, and Japan. In Costa Rica, where rain can fall in sudden torrents and storms build with wild energy, the stage is set for nature to get creative.
What’s the scientific explanation behind this bizarre event?
There are several theories, but none that can explain every case perfectly.
Here’s what scientists believe may be behind worm rain:
- Strong updrafts: Powerful upward wind currents can suck lightweight organisms like worms, frogs, or small fish into the lower atmosphere—especially during intense thunderstorms. These creatures are then carried by the wind and dropped elsewhere when the storm lets go.
- Surface flooding: Tropical downpours often cause temporary flash floods that saturate the ground. Earthworms, unable to breathe in waterlogged soil, squirm to the surface and may be swept into streams, streets, or rooftops by gushing water.
- Disoriented birds: One fringe theory suggests birds may accidentally drop clutches of worms after collecting them for nesting or feeding, though this doesn’t account for the number and timing of the reports.
- Localized phenomenon: Some experts believe what’s perceived as “worm rain” may be a combination of worms escaping flooding and being redistributed in odd places due to the chaotic water flow during torrential rains.
Despite these ideas, none can fully account for why worms would be found in places physically impossible to reach by simple ground flooding, such as on balconies or rooftops, or in closed courtyards.
What do locals believe causes worm rain?
Ask a Tico in the countryside, and you’ll likely get a very different explanation—one rooted in tradition, caution, and respect for nature’s unseen forces.
- The spirits are warning us: In some Indigenous lore, odd events during the rainy season are seen as messages from the spirit world—either warnings or blessings. Rain that falls “wrong” or brings unexpected creatures might mean someone has disturbed the balance.
- Witchcraft or brujería: In areas where belief in brujas still lingers, some say worm rain could be the result of spells or curses, especially if it happens to someone’s home in isolation.
- Signs of a season change: Others simply see it as an old sign of changing weather cycles—evidence that the natural world is adjusting and waking up for the second part of the year.
Whether grounded in belief or biology, the stories are always told with a glint in the eye, as if even the teller knows that Costa Rica’s rain has a mind of its own.
What other weird things happen during Costa Rica’s rainy season?
The worm rain might take the crown for “most unsettling precipitation,” but the wet season has plenty of strange surprises in store for those paying attention.
Here are a few notable oddities:
- Exploding mushrooms – Some rainforest fungi pop open overnight, releasing spores with a gentle puff. Locals sometimes find their yards transformed in 24 hours.
- Frog migrations – Entire swarms of frogs, from red-eyed tree frogs to smoky jungle frogs, cross roads at night en masse, chirping and hopping toward seasonal pools to breed.
- Fish in puddles – Small fish like guppies or even seasonal sardines appear in roadside puddles far from rivers, especially near mangrove estuaries, possibly brought by high tides or storm surges.
- Flying ant swarms (Nuptial Flights) – Right after the first major rain of the season (usually in May), millions of winged ants take flight in a dramatic spectacle of reproduction. Birds go wild during these events.
- Repeat lightning strikes – Certain trees seem to attract lightning multiple times in a season. Known as “lightning trees” in some regions, they’re left charred but still standing.
When and where are you most likely to see these phenomena?
Costa Rica’s rainy season stretches from May to November, with the heaviest rains typically falling between September and October.
If you’re hoping to (or hoping not to) witness these natural curiosities, here’s where to look:
- Caribbean side (Tortuguero, Puerto Viejo) – With more consistent rainfall year-round, this region offers peak oddity potential.
- Osa Peninsula – Remote, wild, and flooded with biodiversity, this is one of the richest places for strange sightings.
- Mountainous zones (Monteverde, Tilarán) – The cloud forests are alive with migrating creatures and unusual weather quirks.
- Lowland valleys and farmlands – These areas often experience worm rains and frog migrations due to their soil composition and proximity to flood-prone rivers.
FAQ: Worm Rains & Wet Season Weirdness
Q: Do worms survive the fall from the sky?
A: Some do if they land on soft ground or leaves, but many perish from the impact or exposure.
Q: Are there documented cases in Costa Rica?
A: Anecdotal reports exist, mostly in rural areas, but formal scientific documentation is scarce.
Q: Could worms crawl up to rooftops during rain?
A: Highly unlikely, especially when found in large numbers on smooth surfaces like metal or tile.
Q: Is worm rain harmful?
A: No, just a bit unsettling—unless you’re a bird or frog who sees it as a buffet.
Q: Are similar events reported elsewhere?
A: Yes, in places like Norway, Japan, and parts of the USA. It’s a global oddity.
Q: What’s the weirdest thing you’ve heard about the rainy season in Costa Rica?
A: One local swears it once rained tadpoles. Another swears a pineapple fell from a cloud. Who’s to say they’re wrong?
