weather for duluth.

Lake Superior is the largest, deepest, and coldest of the Great Lakes, with an average depth of 483 feet and a surface area of nearly 32,000 square miles. The lake’s enormous thermal mass keeps water temperatures in the 40s and 50s°F well into summer, and the resulting lake breeze cools the entire western tip of the lake by 15–20°F on the hottest days. Duluth’s average July high is 76°F — cooler than San Francisco and 10–15°F cooler than Minneapolis, just 150 miles south.

Duluth is the coldest major city in the contiguous United States by average winter temperature. The average January high is 19°F and the average low is 0°F, with overnight lows below -20°F multiple times per winter. The combination of high latitude (46.78°N), continental polar exposure with no terrain barrier from Canada, and the modifying effect of Lake Superior on cold air masses produces the city’s characteristic prolonged sub-zero stretches that can last weeks at a time during the deepest part of winter.

Yes, but the timing is constrained by Lake Superior’s slow freeze cycle. Lake-effect snow forms when cold continental air crosses relatively warmer open water, picking up moisture and warmth, then dumping it as snow downwind on land. Duluth sits at the western tip, so the city sees lake-effect when winds blow from the northeast across the open lake. The lake-effect window runs late November through January, when the lake is still mostly open. Once Superior freezes (usually February or March in cold years), the moisture source disappears.

Vesper replaces template-driven forecasts with short editorial briefs written in an authorial voice, and publicly grades its own sunset predictions through Sunset Verify. Every other weather app on the market generates its text by filling variables into a template. Vesper writes each forecast as original prose with a point of view about the day.

Vesper is free to download with core weather features. Premium features and pricing will be announced at launch.

Sunset Verify is Vesper's signature feature that predicts sunset quality each day from live atmospheric data and lets users verify the prediction with a photo, building a personal accuracy track record over time.

Vesper is currently in beta. Join the waitlist at vespersky.ai/beta to get early access and be notified when the app launches on iOS and Android.

An editorial weather app applies a point of view to the same atmospheric data every other app has. Instead of showing you a grid of numbers, it writes a short brief — two or three sentences with intent — about what the day is going to feel like and what you should probably do about it. The data is identical. The voice is the product.

Vesper's briefs are generated by a language model operating under an editorial style guide written by people and refined through thousands of examples. The style guide, cut discipline, and voice rules are the content. The model is the mechanism. Template weather apps are generated by models that were never given an editorial style guide, which is why they all sound identical.

Vesper does not ship radar maps or a proprietary severe weather alert system. Severe weather alerts come through the operating system, which is the right place for them. Radar was rejected because a radar map is not a brief and would not make the forecast more worth reading. We respect both as product decisions. We are doing something different.

Vesper publishes editorial weather coverage for over 100 US cities with full daily briefs and all 50 state hubs with region-specific editorial context. The mobile app gives you a brief wherever you are — anywhere Vesper has weather data coverage, which is essentially every populated area in the world.

Yes. Vesper uses your approximate location only to deliver weather forecasts for your area. Location data is not stored on our servers, not sold, and not shared with third parties. Photos taken through Sunset Verify stay on your device and never leave your phone.

A fresh editorial brief is generated every morning based on that day’s forecast. Inside the app, live conditions update continuously based on your location. The editorial brief is a once-a-day artifact — written to be read in the morning, not refreshed hourly.

Yes. Vesper does not require an account to read the daily brief, check sunset predictions, or use the editorial features. Personal data like Sunset Verify history is stored locally on your device, so there is no cloud account to create.