weather for st. louis.

St. Louis sits in the Mississippi Valley severe weather corridor, where moist Gulf of Mexico air surging north from the Gulf meets cool, dry continental air from the northern Plains and the Rocky Mountain foothills. The collision typically peaks in April and May when temperature contrasts are sharpest, producing supercell thunderstorms, tornadoes, and damaging straight-line winds. The metro averages 8–12 tornado-warned days per year, with the most destructive recent event being the EF-3 tornado that crossed the metro on Good Friday 2011.

The Missouri River joins the Mississippi just north of downtown, and the combined river surface area produces a significant local moisture source. On cool autumn and winter mornings, water vapor evaporating from the warmer river surfaces condenses immediately in the cooler air above, producing a layer of valley fog that pools through the river bottoms and into the lower elevations of the city. The fog typically lifts within a few hours of sunrise but can persist longer during inversions.

Winter precipitation in St. Louis frequently falls as freezing rain rather than snow because warm Gulf air aloft overrides shallow cold air at the surface. As snow falls into the warm layer it melts, then refreezes on contact with subfreezing surfaces below. The mid-continental position puts the city directly in the path of the warm-air-overrunning pattern that produces ice storms, and the metro sees one or two significant ice events per winter on average. Power outages from accumulated ice on lines and trees are the dominant hazard.

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.