# Thermo Diem

> Compares current 'feels like' temperature to the previous day. (iPhone/iPad app by Basic Function.)

- Source: https://appshunter.io/ios/app/thermo-diem/id912968904 (this page in markdown: same URL + `.md`)
- Developer: [Basic Function](https://appshunter.io/developer/434863190)
- Category: Weather, Utilities
- Price: Free
- Rating: 4.00/5 from 3 App Store ratings · 19 written reviews indexed
- Age rating: 4+
- Requires: iOS 26.0 · 4 MB
- Languages: German (Germany), American English, French (France), European Spanish
- Released: 2014-10-14
- Data updated: 2026-10-12
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/thermo-diem/id912968904/reviews.md

## What is Thermo Diem?

Most weather apps give you numbers. Thermo Diem gives you context.

A 72° day after a week of freezing cold feels completely different than 72° after a scorching heat wave. That’s because human comfort is relative — your physiology adapts to what you experienced yesterday.

Thermo Diem compares current apparent temperature directly to yesterday, tomorrow, and future days of the week, answering the only question that matters when stepping outside: "How does today feel compared to yesterday?"

THE SCIENCE OF APPARENT TEMPERATURE
Ambient air temperature only tells half the story. Thermo Diem implements advanced biometeorological models (NOAA Wind Chill, Rothfusz Heat Index, and Steadman’s psychrometric heat balance) — calculating the thermodynamic balance between human skin and the surrounding atmosphere:
• Vapor Pressure & Humidity: Accounts for evaporative cooling resistance.
• Wind Velocity: Measures forced convective heat loss from exposed skin.
• Direct Solar Radiation: Incorporates direct thermal gains from daylight and UV index.
The result is true Apparent Temperature, evaluated directly against your recent baseline.

7 INTUITIVE SHIFTS
Pure clarity with zero clutter:
• Much Warmer
• Warmer
• A Little Warmer
• About The Same
• A Little Cooler
• Cooler
• Much Cooler

TREND CURVES & FUTURE SHIFT
See today’s feels-like trajectory overlaid directly on yesterday’s curve. Use the 7-day Future Shift dial to scrub ahead and compare any upcoming hour or day of the week against right now or yesterday's high.

CARPLAY, DYNAMIC ISLAND & LIVE ACTIVITIES
Get temperature shift intelligence wherever you are. Thermo Diem brings real-time relative temperature and color-synchronized spectrum gauges to your CarPlay Dashboard, iPhone Lock Screen, and Dynamic Island—keeping you informed before your commute begins.

HOME & LOCK SCREEN WIDGETS
Bring iconic poster typography to your Home Screen and Lock Screen. Features bold, edge-to-edge circular lock screen widgets maximized for instant legibility, split overview cards, and signature spectrum slider gauges. Long-press any widget to customize comparison targets and display details.

STANDALONE APPLE WATCH APP
Designed natively for your wrist. Check today's shift at a glance with rapid launch, custom watchOS complications (Corner, Circular, Rectangular, Inline), and independent background updates.

NATIONWIDE MOVERS
Curious where the biggest swings are happening? Explore 24-hour temperature movers across major climate regions nationwide.

NOW IN 4 LANGUAGES
Full native support for English, Spanish, French, and German.

PRIVACY FIRST
No tracking, no third-party ad networks, and no data harvesting. Just clean, honest weather intelligence.

## Key features

- Compares today's 'feels like' temperature to yesterday
- Provides 7 relative temperature descriptions
- Considers humidity, wind, dew points, and temperature
- Designed for Apple Watch
- Uses Forecast.io data

## Recent user reviews (10 of 19)

All indexed reviews: https://appshunter.io/ios/app/thermo-diem/id912968904/reviews.md

### 2/5 — Widget not current

*2026-10-08*

After I click on widget, only then it updates to the current weather. This defeats the purpose of being able to glance at the widget and have current information.

### 5/5 — Julia

*2026-09-30*

I love this app I really recommend it for people who are on the go because it is easy to see it right away and compare today and the next days temps guys get it!!!!!😭🙏

### 5/5 — 3.2 is a Game Changer

*2026-09-24*

Works on all of your devices

### 2/5 — apparently 90 is cooler than 78

*2019-07-20*

For a while this app would always say “today is warmer” I kind of forgot about it until a couple days ago. The high was 78. The next day was in the mid 90s, yet the app kept saying “today is cooler”

### 1/5 — Always warmer

*2019-05-17*

All this app ever tells me is that today will feel warmer than yesterday. Every day.

### 2/5 — Eh.

*2017-09-22*

This is a very good idea, however it’s not always accurate.

### 2/5 — Widget broken

*2017-04-06*

Great idea for an app. But the widget isn't updating and that's kinda the whole point.

### 1/5 — Not accurate

*2017-03-11*

TODAY IS ALWAYS SIMILAR TO YESTERDAY. I have yet to see a difference. I live in Maryland with drastically different temperatures such as two days ago being 67 and the following day in the 30s. And "today will feel similar to yesterday". Never a change, ever. A lot of times yes today is the same forecast but often times it is 20-30 degrees warmer or colder and no change. Hate this app. It's useless.

### 2/5 — Poor today widget and Watch extension

*2016-02-28*

The today's notification widget and the actual app info is never aligned. Meaning the today widget will say "tomorrow will feel like today" and when you open the actual app it will say "tomorrow's will feel much cooler". 
This happens almost every time. 
Same issue with Watch extension. 

Simple app like this should be in sync.

### 3/5 — Unreliable Today widget

*2015-10-06*

It's a good app, but not one I'm likely to bother opening. However, the Today widget I check each day, but after a while it gets stuck and doesn't update. The problem with this is that you don't know it's stuck and not giving the correct information without opening the app which I wouldn't normally bother doing. It needs an update date in the Today widget. The same is true for the Watch app.

## Frequently asked questions about Thermo Diem

### What does Thermo Diem compare?

Thermo Diem compares today's 'feels like' temperature to how it felt 24 hours ago. It takes into account factors like relative humidity, wind, dew points, and temperature to provide a relative sense of warmth or coolness.

### How does Thermo Diem describe the temperature changes?

Thermo Diem provides seven simple outputs: Much Warmer, Warmer, Slightly Warmer, Similar, Slightly Cooler, Cooler, and Much Cooler. This offers a quick, relative understanding of the day's weather feel.

### What data source does Thermo Diem use?

Thermo Diem utilizes data provided by Forecast.io, which is described as a highly accurate weather reporting service.

### Is Thermo Diem available on other devices besides Apple Watch?

The description specifically highlights that Thermo Diem is designed for the Apple Watch, suggesting it is optimized for or primarily available on that platform.

### What is the formula used by Thermo Diem?

Thermo Diem uses the formula AT = -2.7 + 1.04*T + 2.0*e -0.65*v, where AT and T are in degrees Celsius, e is vapor pressure in kPa, and v is 10m wind speed in m/sec.

### How often is Thermo Diem updated?

The latest version, 2.1, was released on June 4, 2015. This indicates that updates may not be very frequent, with the last update being several years ago.

### What is the user rating for Thermo Diem?

Thermo Diem has a rating of 1.5 stars based on 6 ratings. This suggests a generally negative user sentiment based on the limited feedback available.

### Does Thermo Diem have ads?

The provided data does not specify whether Thermo Diem contains advertisements. However, it is a free application, which sometimes correlates with ad support.

## Version history (last 5 releases)

### 3.5 — 2026-10-05

What's New in Version 3.5:
   • Home Screen Quick Actions: Long-press (Haptic Touch) the app icon to jump to Tomorrow's Forecast, Nationwide Movers, or activate your Commute Live Activity.
   • Reliable Widget Scheduling: Improved background refresh cadence for Lock Screen and Home Screen widgets.
   • Tomorrow Outlook Polish: Smoother transitions and refined typography when previewing tomorrow's temperature shift.
   • Performance & Stability: Memory optimizations and background task reliability enhancements.
   • MacOS version
• What's New in Version 3.4:
   • Commute Live Activity & Dynamic Island drive tracking.
   • Smart automatic background refresh scheduled before morning waking hours.
   • Deeper solar radiation and wind gust biometeorology modeling.
• What's New in Version 3.3:
   • Multilingual support (Spanish, French, German).
   • Editorial headline grammar refinements ("About the same as yesterday").
   • Streamlined city and US state abbreviation labels.
• What's New in Version 3.2:
   • Nationwide Movers: Real-time leaderboard tracking the largest 24-hour temperature swings across the country.
   • Quick City Switcher to view any mover's climate delta.
   • Enhanced Apple Watch Ultra and Series contrast.
• What's New in Version 3.1:
   • Interactive 24-hour horizon scrubber to compare future hours with yesterday.
   • Peak comparison toggle: "Same Time" vs. "Yesterday's High".
   • Dynamic high-contrast palettes for extreme shifts.
• What's New in Version 3.0:
   • Complete ground-up redesign with bold Anton typography.
   • NOAA-grade biometeorological apparent temperature engine.
   • Native standalone Apple Watch app with gauge needles.
   • Modern Lock Screen and Home Screen widgets.

### 3.4 — 2026-09-29

What's New in Version 3.4

• Bigger, Bolder Lock Screen Widget: Completely re-engineered circular lock screen widget with an edge-to-edge layout that dramatically expands font sizes for instant, glanceable legibility.
• Synchronized Spectrum Slider: Fine-tuned the color spectrum bar across Live Activities, widgets, and the main app so the needle position precisely mirrors your feels-like tier and headline accent color.
• Lock Screen & CarPlay Polish: Enhanced contrast, refined delta badges, and smoother real-time commuter updates

Also recently added in 3.0:
• Multilingual Localization (3.3): Full native support for Spanish, French, and German with tailored editorial grammar.
• CarPlay Commute Integration (3.2): Live temperature comparison banner directly on your vehicle dashboard.
• Nationwide Movers (3.1): Live tracker uncovering which cities experienced the biggest 24-hour temperature swings.
• Complete 3.0 Redesign: Advanced NOAA biometeorological modeling (Wind Chill, Heat Index, and Solar Radiation), 24-hour interactive comparison horizon, Dynamic Island Live Activities, and a companion Apple Watch app with wrist complications.

### 3.3 — 2026-09-26

What's new in 3.3:

• Multi-Language Support: Thermo Diem is now fully localized in Spanish, French, and German!
• Editorial Headline Grammar: Streamlined comparison phrasing with natural equative logic ("About the same as yesterday").
• Precision Weather Integrity: Enhanced data consistency across Home Screen widgets, Apple Watch complications, and CarPlay Live Activities.
• Performance & Dynamic Type: Faster optical caching for instant font rendering.

### 3.2.2 — 2026-09-26

What’s New in Version 3.2.2

• Redesigned Lock Screen Live Activity: Live Activities now feature our signature bold typography, large glanceable temperature, signed shift badge, and full-width color spectrum bar right on your Lock Screen.
• Celsius & Metric Accuracy: Fixed temperature calculations for Celsius users and added metric wind speeds (km/h) for accurate global biometeorology.
• Auto-Switch in Evening: Added a new setting under Preferences to automatically flip your comparison to tomorrow in the evening (with customizable switch time) and reset to yesterday each morning.
• Latest iOS Refinements: Visual and performance optimizations for the latest iOS updates across Lock Screen, Dynamic Island, and CarPlay.

### 3.2 — 2026-09-24

• CarPlay Dashboard Support:
View relative temperature shifts directly on your vehicle’s dashboard with responsive layouts and our signature temperature spectrum gauge.

• Future Shift (7-Day Horizon Scrubber):
Compare any upcoming hour or day of the week against Right Now, Yesterday at this time, or Yesterday’s High to know how it will feel before you head out.

• Customizable Widgets ("Edit Widget"):
Long-press any Thermo Diem widget on your Home Screen to customize your comparison target (Automatic, Yesterday, or Tomorrow) and toggle the spectrum bar or reference details.

• Atmosphere & Science Breakdown:
Deep dive into humidity, wind chill, dew point, and heat index to see exactly what is driving today's feels-like temperature.

• Nationwide Temperature Movers:
Discover which cities across the country are experiencing the most dramatic temperature shifts today compared to yesterday.

• Design Polish:
Refined layout spacing and optical alignment across all Home Screen widgets and Apple Watch complications.

## Apps similar to Thermo Diem

| App | Rating | Price | Category |
| --- | --- | --- | --- |
| [Wilitrain](https://appshunter.io/ios/app/wilitrain/id6753659941) | — | Free | Weather |
| [AQI Me](https://appshunter.io/ios/app/aqi-me/id6793547564) | — | Free | Weather |
| [Gulldodo: Air Quality & Pollen](https://appshunter.io/ios/app/gulldodo-air-quality-and-pollen/id6775039172) | — | Free | Weather |
| [AirGuard: AQI & Air Quality](https://appshunter.io/ios/app/airguard-aqi-and-air-quality/id6771846945) | — | Free | Weather |
| [Odd Weather](https://appshunter.io/ios/app/odd-weather/id6777082926) | — | Free | Weather |
| [umbrella · will it rain](https://appshunter.io/ios/app/umbrella-will-it-rain/id6778637758) | 5.0 (1) | Free | Weather |

## More apps by Basic Function

- [Hungry Lizards](https://appshunter.io/ios/app/hungry-lizards/id525416212)

All apps by Basic Function: https://appshunter.io/developer/434863190

## Related topics

[delorenzo](https://appshunter.io/ios/topics/delorenzo)

---

*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-10-12.*