About Tenki Link
We started Tenki Link because we were tired of weather forecasts that treated Tokyo like a single point. The JMA reports a temperature for "central Tokyo" and everyone from Nerima to Koto is supposed to accept it as their reality. But it's not. On a still August afternoon, the difference between Shinjuku and Nerima can be 5 degrees Celsius. The difference between Shinagawa and Nakano can determine whether you need a jacket or wish you'd worn shorts. And the "Tokyo" forecast captures none of it.
So we built something different. A network map that shows six nodes across the 23 wards, connected by the temperature differences that actually matter. Live data from the Open-Meteo API, updated every time you load the page. Essays that trace how heat flows, how the bay breeze pushes inland, how river corridors channel wind, and how mountain gaps connect the city to the outside weather. This isn't a weather service. It's a field guide to a connected system.
What We Believe
Tokyo's weather isn't 23 separate forecasts. It's one system with 23 expressions. The heat island in Shinjuku drives flows that affect Koto 8 kilometers away. The bay breeze that cools Shinagawa at 10:30am is the same air mass that might reach Shinjuku by 2pm if the pressure gradient is strong enough. The cold air that pools in Nerima on a January morning came through the Tama River gap from the Okutama mountains, and its journey is traceable if you know where to look.
We believe in systems thinking applied at the street level. Not abstract climate models — though we respect those — but observable, walkable, cyclable weather patterns that you can feel on your skin and verify with a thermometer. We believe that the best way to understand a city's climate is to move through it, note the shifts, and connect the dots. That's what we do. That's what this site is for.
We also believe in transparency. Every temperature reading on our network comes from a real API call to Open-Meteo, fetched when you load the page. We don't use cached data unless the API is temporarily unavailable. We don't adjust numbers to make them look cleaner. If the API fails, we show "Updating..." — never a fake static number. Our methodology is documented on our How We Link page, and our corrections are logged on the Fix Log.
The Team
Sora Tanaka
Sora mapped Tokyo's pedestrian wind corridors for a master's thesis at the University of Tokyo and never stopped noticing how air moves through the city. He cycles 30 kilometers daily — from Koenji to the bay and back — logging temperature shifts with a pocket thermometer and a notebook. The idea for Tenki Link came from five years of these rides, during which he realized that the "Tokyo" forecast had almost nothing to do with the weather he was actually experiencing on the road.
Maya Lin
Maya models urban heat flows for a living — her day job involves thermal simulation for city planning projects across East Asia. She joined Tenki Link because she wanted to apply the same modeling principles to something public-facing and practical. She applied her professional heat flow models to her own commute (Shimokitazawa to Marunouchi) and discovered that the 2.5-degree temperature drop she felt every evening at Yoyogi was predictable, replicable, and entirely absent from every weather app she checked.
Ren Kobayashi
Ren knows every cool route through the 23 wards because he's ridden them all — twice a day, six days a week, for three years. He delivers packages for a living and has developed an encyclopedic knowledge of Tokyo's thermal landscape: which alleyways in Shinjuku trap heat until 9pm, which riverside paths in Koto are 3 degrees cooler at noon, which underpasses in Shibuya create sudden wind tunnels. His field notes form the observational backbone of our Heat Flow and River Corridors essays.
How We Work
Tenki Link is a small operation. We're three people with day jobs who maintain this site because we think the information matters. Sora writes the essays and manages the data pipeline. Maya builds the thermal models and verifies our scientific claims. Ren contributes field observations and tests our theories against the reality of cycling through the city at different times of day.
Our six network nodes correspond to actual points in space — specific latitudes and longitudes within each district — and the temperature data comes from the Open-Meteo API's forecast endpoint. We chose Open-Meteo because it's free, requires no API key, and provides high-resolution data based on numerical weather models. The API doesn't give us historical data (we'd need a paid service for that), but it gives us current conditions and short-term forecasts that are accurate enough to show the temperature differences between districts.
The line thickness and colors on our network map are calculated client-side in your browser. We fetch the temperature for each node, compute the absolute difference between every pair, and render SVG lines with widths and colors that correspond to those differences. No server processes your data. No analytics track your movement across the map. The entire calculation happens in your browser using JavaScript that you can read in our main.js file.
Why We Built This
There's a gap between professional meteorology and everyday weather experience. The JMA does excellent work — their models are sophisticated, their forecasts are reliable at the regional scale, and their warnings save lives. But the gap between "Tokyo 23 wards" and "the weather on my street" is real, and it's getting wider as the city heats up and the microclimates diverge.
We built Tenki Link to fill that gap. Not with a competing forecast — we don't have the resources for that — but with a systems perspective that shows how the city's weather connects. When you see that the line between Shinjuku and Koto is thick and red, you understand that those two districts are in different thermal regimes. When you see that the line between Shinagawa and Shinjuku is thin and lavender, you know the bay breeze has connected them. The network doesn't replace the forecast. It contextualizes it.
We also built this because we think more people should experience Tokyo as a thermal landscape. The city changes character as you move through it — not just culturally and architecturally, but climatically. A commute that crosses two or three thermal zones is a daily encounter with a complex system that most residents never consciously register. We want to make that system visible, legible, and maybe even beautiful. The lavender lines on our network map are data. But they're also a kind of poetry — a diagram of connections that exist whether you look at them or not.
Contact
We'd love to hear from you — especially if you've noticed a temperature shift on your own commute that we haven't documented. Flow tips, route shares, corrections, and collaboration ideas are all welcome.
Reach us at connect@tenkilink.com or through our contact form. We read everything, though we can't always respond quickly — this is a side project, and our day jobs keep us busy.