Which Is Colder: Minus 40°C or Minus 40°F? Explained

When you hear about extreme temperatures like –40°C and –40°F, it’s natural to wonder which one is colder. Celsius and Fahrenheit are two different scales, and they usually give very different numbers for the same temperature. But the answer here is surprising:

Minus 40°C and Minus 40°F are exactly the same temperature.

This guide explains why the two scales meet at –40, how it affects everyday life, and why it matters for weather, travel, and even laundry.

Why –40°C Equals –40°F

Celsius and Fahrenheit are based on different reference points:

Celsius (°C)

Water freezes at 0°C

Water boils at 100°C

Fahrenheit (°F)

Water freezes at 32°F

Water boils at 212°F

Because the scales increase at different rates, their numbers almost never match.
However, mathematically, there is one single temperature where both scales show the same value.

That temperature is –40.

It is the only point at which Celsius and Fahrenheit are numerically equal.

Which Is Colder: –40°C or –40°F?

The short answer: neither. They’re equally cold.

At –40:

• Skin can freeze in minutes.
• Exposed areas risk frostbite almost instantly.
• Boiling water thrown in the air can turn into ice mist.
• Car engines may fail to start.

This temperature is typical in Russia, Canada, Alaska, Sweden, and Mongolia during peak winter.

How to Convert °C to °F and Vice Versa

• Formula to convert Celsius to Fahrenheit:
  °F = (°C × 9/5) + 32
• Formula to convert Fahrenheit to Celsius:
  °C = (°F − 32) × 5/9

Common Temperature Reference

What Does –40 Feel Like in Real Life?

To give you an idea, -40 feels much colder than a typical winter day. It’s the kind of cold that stings your face, makes it hard to breathe deeply, and freezes exposed skin almost instantly.

In many places, schools close, flights are canceled, and people are warned to stay indoors when temperatures drop to this level. It’s far beyond regular winter cold, it’s a level that demands caution and preparation.

Why Do Celsius and Fahrenheit Meet at –40?

Celsius and Fahrenheit are based on different reference points. Celsius sets freezing at 0 and boiling at 100. Fahrenheit sets freezing at 32 and boiling at 212. Because of this, the scales usually show very different values for the same temperature.

But due to how both scales are structured, there’s one temperature where their paths cross: –40. It’s the one place on the scale where both systems agree. You don’t need to convert anything at –40, Celsius and Fahrenheit are the same.

Why Do Celsius and Fahrenheit Meet at –40?

This happens because of how the two scales are structured mathematically.

• Fahrenheit degrees are smaller than Celsius degrees
• The two scales start at different zero points
• When plotted on a graph, their lines cross once and only once

That crossing point is –40.
Every other temperature requires conversion.

What About –4°C? Is That Freezing?

Yes, –4°C is below the freezing point of water, which is 0°C. This means:

• Roads can be icy
• Puddles and pipes may freeze
• You’ll definitely need a jacket outdoors

In Fahrenheit, this temperature is just slightly above 24 degrees, still cold, but much milder than –40. It’s a common temperature in many places during winter.

Where in the World Does It Reach –40?

Temperatures of –40°C (or –40°F) are not just theoretical, they occur regularly in some of the coldest inhabited regions on Earth, mostly during peak winter.

Places that commonly experience –40 temperatures:

Yakutsk, Russia
One of the coldest cities on Earth, where winter lows often dip below –40°C.

Fairbanks, Alaska (USA)
In deep winter, temperatures in interior Alaska can hit –40°F.

Yellowknife, Canada
Northern territories like Yukon and Northwest Territories frequently face –40°C/F.

Ulaanbaatar, Mongolia
High-altitude, landlocked geography contributes to long sub-zero winters.

In these regions, residents take special precautions like:

• Plugging in engine block heaters
• Wearing triple-layered insulation
• Using high-alcohol fuels to prevent freezing

Why This Matters in Daily Life

Understanding Celsius vs Fahrenheit isn’t just trivia, it helps when:

• Checking international weather forecasts.
• Traveling across countries that use different scales.
• Setting correct laundry machine temperatures.
• Explaining extreme weather conditions clearly.
• Knowing that –40°C = –40°F helps you instantly recognize just how cold it really is.

Key Facts to Remember

• Minus 40°C is the same as minus 40°F, this is a rare match between the two scales
• Both represent extreme cold that is hazardous to health and daily life
• 40°C in washing machines means a warm, everyday laundry setting
• –-4 °C is a typical winter temperature, below freezing, but not dangerously cold

Final Thoughts

–40°C and –40°F feel the same because they are the same — brutally cold.

It’s one of those rare moments where science doesn’t complicate things, it brings clarity. Whether you're checking the forecast, packing for a trip, or trying to make sense of your washing machine settings, knowing just a few key temperatures can make life a lot easier.

You don’t need to remember formulas or do mental math. Just know this:
–40 is cold, no matter where you are or how you measure it.
40°C is warm — but only in your laundry, not on the street.

Sometimes, the numbers speak for themselves. And when they don’t, now you know how to read them.

Frequently Asked Questions (FAQ)

Q1. Why do Celsius and Fahrenheit only match at –40?
Because of how their scales are structured. At –40, both formulas yield the same value.

Q2. How dangerous is –40 in daily life?
At –40, exposed skin can freeze in under 10 minutes, making it a severe health hazard.

Q3. Is –20°C the same as –20°F?
No. –20°F equals –28.9°C, which is significantly colder than –20°C.

Q4. Why is 40°C on laundry machines considered “warm”?
Because it balances fabric care with effective stain removal without causing damage.