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Reading the weather · 4 min · 4 steps

The daily swing

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Goal. Use the forecast timeline to see why some places swing more than others between day and night.

Coming soon to the App Store

Steps

  1. Predict

    Over the next day, where will the temperature change most between afternoon and night?

    • On a small island in the ocean
    • In a desert far from the sea
    • Both the same
    Show the answer

    In a desert far from the sea. In the desert: dry ground and clear skies heat up fast by day and lose heat fast at night.

    Press play on the timeline and watch the pills change hour by hour. By the sea the numbers change slowly; inland, and above all in deserts, they swing much more.

  2. Clear, dry air lets the ground lose its heat to space at night, so deserts can be very hot by day and cold before dawn. Humid air and clouds act like a blanket and keep the night warmer.

  3. Taiwan's coastal cities usually swing by only about 5 to 8 °C between day and night, because the nearby sea and the humid air even out the temperature.

  4. The warmest time of day is usually mid-afternoon, not noon: for a few hours after the Sun is highest the ground still takes in more heat than it loses. The coldest time is around sunrise.

The common mistake

Myth

The hottest time of the day is noon, when the Sun is highest.

Fact. The ground keeps gaining more heat than it loses until mid-afternoon, so the air is usually warmest around 2 to 4 pm and coldest around sunrise.

Check yourself

Question 1

Why do deserts get so cold at night?

  • Dry, clear air lets heat escape to space
  • The sand reflects moonlight
  • Cold wind blows in from the sea
Show the answer

Dry, clear air lets heat escape to space. Without clouds or water vapour to hold it in, the heat of the day radiates away to space.

Question 2

When is it usually warmest during the day?

  • At sunrise
  • At noon
  • In mid-afternoon
Show the answer

In mid-afternoon. The temperature keeps rising while the ground gains more heat than it loses, usually until mid-afternoon.

Question 3

Why does a cloudy night stay warmer?

  • Clouds trap heat leaving the ground
  • Clouds make their own heat
  • Clouds block the Moon's cold light
Show the answer

Clouds trap heat leaving the ground. Clouds absorb the heat radiated by the ground and send part of it back down.

Words in this lesson

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Curriculum

Taiwan 12-year curriculum (108 課綱), natural science
Id-Ⅳ-2
US Next Generation Science Standards
MS-ESS2-5
England national curriculum
KS3 Geography: weather and climate