Checking the weather only helps if you understand the numbers. Most of the world uses Celsius, but the United States (and a few others) use Fahrenheit — so packing the wrong clothes because you misread the forecast is a classic travel mistake.
What each temperature feels like
| °C | °F | Feels like |
|---|---|---|
| 0°C | 32°F | Freezing — heavy coat |
| 10°C | 50°F | Cool — jacket |
| 20°C | 68°F | Mild & pleasant |
| 30°C | 86°F | Hot — shorts & sunscreen |
| 37°C | 98.6°F | Body temperature — very hot day |
Mental shortcuts
The exact formula is °F = (°C × 9/5) + 32, but for a quick estimate just double the Celsius and add 30 (so 20°C ≈ 70°F — close to the real 68°F). Going the other way, subtract 30 and halve. A few anchors help too: 0°C = 32°F (freezing), 10° = 50°, 20° = 68°, 30° = 86°. Memorise those four and you can place almost any forecast instantly.
Convert a temperature
For exact figures, type a number, choose the unit, and read off the equivalents.
Temperature → °C, °F, K + a feel
Why it matters for packing
- Read the forecast in the local unit — a US forecast in °F vs a European one in °C can mislead you completely.
- Check day and night — deserts and high-altitude places swing hugely between hot days and cold nights.
- Set your weather app to the local unit while travelling so it matches signs and news.
- Remember humidity — 30°C in a dry climate feels very different from 30°C in the tropics.
Go deeper
Questions
How do I quickly convert Celsius to Fahrenheit?
For a fast estimate, double the Celsius and add 30 (20°C → about 70°F). The exact formula is (°C × 9/5) + 32, which gives 68°F — the shortcut is close enough to know how to dress.
Which countries use Fahrenheit?
The United States is the main one travellers encounter, along with a few small territories. Almost everywhere else uses Celsius, so be ready to switch your thinking when travelling to or from the US.
Is 30 degrees hot or cold?
It depends on the unit! 30°C is hot (86°F) — shorts and sunscreen weather. But 30°F is below freezing (about −1°C). This is exactly why reading the forecast in the right unit matters so much for packing.
What temperatures should I pack for?
Check both the daytime high and night-time low for your dates, in the local unit. Pack layers if there's a big swing, and remember humidity makes warm temperatures feel hotter and cold ones feel damper than the number suggests.
At what temperature does water freeze in each scale?
Water freezes at 0°C, which is 32°F, and boils at 100°C / 212°F. The 0°C = 32°F anchor is the most useful one to memorise, since it tells you instantly whether a Fahrenheit forecast is above or below freezing.
Should I change my phone's weather units?
It helps to set your weather app to the local unit while travelling, so your forecast matches local news, signs and conversations. Switch it back when you return home if you prefer your usual unit.
Conversions and "feels like" descriptions are general guides; perceived temperature also depends on humidity, wind and sun. Use the converter for exact figures and check a local forecast for your dates.