The Celsius & Fahrenheit Field Guide

By Felsius – Updated Feb 2026

If someone texts you “it’s 68°F today” and you have to pause to figure out if that’s good news, you’ve come to the right place.

The Basics

Why Celsius and Fahrenheit Feel So Different
Numbers shape how we feel about temperature. Here's why switching can feel so tricky.
Why Build a Weather App That Shows Celsius and Fahrenheit?
Switching settings can get tiresome. What it actually means to see °C and °F together.
Why We Misjudge Temperature When Switching Units
The cognitive mechanics behind anchoring errors when we convert quickly in our heads
Why Fahrenheit Feels More Precise (Even When It Isn't)
A look at why people defend Fahrenheit, and what precision actually means in practice.

How Hot Is 40°C, Really?
Above body temperature and into extreme territory. What actually happens at this threshold.
How Hot Is 35°C, Really?
The step-change beyond 30°C – where heat stops being uncomfortable and starts being an argument.
How Hot Is 30°C, Really?
Summer confusion, humidity effects, and why your Fahrenheit intuition keeps getting this one wrong.
How Hot Is 25°C, Really?
Mild warmth calibration – why 25°C in the shade feels nothing like 25°C in direct sun.
What Does 20°C Actually Feel Like?
The exact temperature that confuses most people, sitting right at the edge of jacket-or-no-jacket.
What Is Room Temperature (and Why No One Agrees)
Science, kitchens, labs, and homes all have different answers. Here's why "room temperature" is vague by design.
How Cold Is 10°C, Really?
Why 10°C feels colder than you expect and when a jacket stops being optional.
How Cold Is 5°C, Really?
Properly cold – and why damp air makes it significantly harder than the number suggests.
How Cold Is 0°C, Really?
The freezing point. What actually changes at 0°C and why some 0°C days feel much colder than others.

Living Between Celsius and Fahrenheit
For expats, travellers, and international couples – the hidden cognitive cost of a daily translation problem.
Why Converting Temperatures All Day Is Mental Overhead
Every conversion is a small draw on attention. Here's why that adds up more than you'd expect.
Why Temperature Numbers Don't Map Cleanly to Comfort
The same number feels different based on humidity, wind, and what you've been calibrated to. Here's why.
Why "Feels Like" Temperature Often Makes Things Worse
The apparent temperature metric sounds helpful but often just adds confusion. Here's what it actually measures.
Why Americans Struggle With Celsius (and Why That's Normal)
It's not ignorance – it's how temperature intuition actually works. A fair-minded look at the switch.
Why Most Weather Apps Make Temperature Harder Than It Needs to Be
The single-country assumption baked into most apps – and what a different design looks like.

Why −40° Is the Same in Celsius and Fahrenheit
The one point where both scales meet. It's easier to understand than you'd think.

The What to Wear Temperature Guide
Does 15°C mean t-shirt weather or mild hypothermia? Use our interactive guide.

This Field Guide is written by the team behind Felsius.
Felsius is the weather app that shows Celsius and Fahrenheit together.