Event · Citizen Science
City Nature Challenge
Every spring, cities across the country compete to find and photograph the most wildlife in four days, and any family with a phone can join in. The City Nature Challenge turns a walk around the block into a genuine scientific expedition. This guide covers when it happens, how to participate through iNaturalist, and how to build a full weekend around the hunt.
This page from Outside, the family adventure app, covers the City Nature Challenge, an annual global citizen science event held each spring in which cities compete to document the greatest number of wild species using the iNaturalist app. The guide explains what the event is, when observation and identification windows occur, how families with children ages 4 to 14 can participate, and how to plan a rewarding weekend of urban nature exploration around the challenge. Key facts include the four-day observation period, the free iNaturalist platform, and the value of urban biodiversity documentation for real scientific research.
| Cost | Free |
|---|---|
| Region | Nationwide and global |
| Season | Late April |
| Best ages | 4 to 14 |
| App required | iNaturalist (free) |
What the City Nature Challenge is
The City Nature Challenge is a worldwide citizen science competition held every spring. Cities organize their residents to go outside and document as many wild plants, animals, fungi, and other organisms as they can find within city limits. Every observation gets submitted through iNaturalist, a free app that connects your photo to a database used by researchers around the world.
The event runs on a split schedule: a four-day observation window followed by several days for the community to help identify what everyone found. At the end, cities compare tallies. The winner is the city with the most observations, the most species, or the most participants, depending on the category. But the real prize is a snapshot of urban nature that scientists actually use.
When it happens every year
The City Nature Challenge takes place in late April each year, typically across the last weekend of the month and into the following Monday or Tuesday. The observation period usually runs Friday through Monday. The identification period, when participants and expert volunteers help name what was found, follows immediately and lasts about a week.
Dates shift slightly from year to year, so check the official City Nature Challenge website or your local participating city's natural history museum or nature center for confirmed dates each spring. Many cities announce their local kickoff events several weeks in advance, which gives families time to plan a full weekend around it rather than scrambling to participate on the last day.
How families take part
Participation is straightforward. Download iNaturalist for free on any smartphone, create a family account, and head outside during the observation window. Photograph anything wild: a sparrow on a fence, a dandelion pushing through a sidewalk crack, a moth resting on a porch light. The app walks you through uploading each photo and suggests an identification based on what it sees.
Kids as young as four can spot and point while an older sibling or parent photographs. Children eight and up can run the app themselves with a little coaching. The identification phase, which runs after the observation window closes, is a great low-energy activity for a rainy afternoon. Families scroll through other people's observations and vote on suggested identifications, which counts as genuine scientific contribution.
Planning your City Nature Challenge weekend
Treat the observation weekend like a field expedition. Pick two or three spots in your city that offer different habitat types: a park with trees, a creek corridor or drainage path, and a neighborhood block with gardens or vacant lots. Variety in habitat means variety in species, and variety in species means a more interesting tally.
Start each outing in the morning when birds are active and insects are warming up. Bring a hand lens or magnifying glass for the younger kids; tiny things like pill bugs, lichens, and leaf galls are all valid observations and reliably delight children in the four-to-eight range. Pack a field lunch and make an afternoon of it. Log your observations together that evening so kids can see their finds appear on the city-wide map in real time.
Why it matters beyond the competition
Cities are not ecological deserts. Research consistently shows that urban green spaces, street trees, drainage corridors, and even backyard gardens support a remarkable range of native species. The City Nature Challenge generates tens of thousands of verified observations each year that researchers use to track migration patterns, monitor invasive species, and understand how wildlife adapts to human-dominated landscapes.
For kids, understanding that their observation is a real data point changes the nature of a walk. They are not just looking; they are contributing. That shift from tourist to participant is one of the most powerful things a family can cultivate in the outdoors, and the City Nature Challenge delivers it without any special gear, training, or budget.
Getting the most out of iNaturalist before the weekend
Spend fifteen minutes with the app before the challenge begins. Set up your account, practice photographing a houseplant or a weed in the yard, and browse the Explore map to see what other people have found in your city in past years. This preview gives kids a sense of what is possible and often sparks a target species, something specific they want to find over the weekend.
Join your city's official City Nature Challenge project within iNaturalist so your observations are automatically counted toward the city's total. Your local natural history museum, nature center, or parks department almost always maintains this project page and may host guided walks or identification workshops you can attend as part of the weekend.
Write about the most surprising thing your family found during the City Nature Challenge. Where were you when you spotted it, what did it look like up close, and what did you learn about it afterward?
Frequently asked questions
Do we need to be experts to participate in the City Nature Challenge?
No expertise is required. iNaturalist suggests identifications automatically based on your photos, and the community helps confirm or correct them during the identification window after the observation period ends. Families new to nature identification are welcome and expected.
What counts as a valid observation?
Any wild organism qualifies: birds, insects, plants, fungi, spiders, and even organisms like lichens or mosses. The animal or plant needs to be wild and uncontained, so a pet or a plant in a pot does not count, but a weed growing through a sidewalk crack absolutely does.
Can we participate if our city is not officially in the competition?
Yes. iNaturalist is always open, and your observations still contribute to the global dataset. Check the City Nature Challenge website each spring for the current list of participating cities. The list grows every year, and many cities join for the first time with little advance notice.
How do we find out the exact dates for this year?
The official City Nature Challenge website announces confirmed dates each spring, usually by late February or early March. Your local natural history museum, parks department, or nature center is also a reliable source and often posts local event schedules tied to the challenge weekend.