• Question: Why does red sky at night mean good weather the next day

    Asked by 10216mw to Mark, Matthew, Mike, Paul, Sabina on 11 Mar 2014.
    • Photo: Matthew Malek

      Matthew Malek answered on 11 Mar 2014:

      It doesn’t really mean this will happen, you can have a red sky at night and lousy weather the next day.

      The red sky at sunset is caused by the long path that light has to travel through the atmosphere when the sun is close to the horizon. The extra distance scatters away the bluer light, leaving the red behind.

      I think that this saying arose because if you can see the red sky at sunset, then there are clear skies. Otherwise you would only see grey clouds! So if the sky is clear at sunset, perhaps it will be clear the next day, too?

      Of course, it might… but clouds can move in at night, so it might not. Fortunately, our knowledge of meterology and weather forecasting has gotten a bit better since then!

    • Photo: Mike Lee

      Mike Lee answered on 11 Mar 2014:

      The Sun sets in the West, which is also where most of the UK weather comes from. So to see a red sky at sunset means the weather coming in is clear, good weather. As Matthew says, it doesn’t always work as weather is far more complicated than that!

    • Photo: Mark Jackson

      Mark Jackson answered on 12 Mar 2014:

      I was surprised to learn that this is one of the few bits of weather folklore which happens to be true, as explained by the other scientists. It seems that there are equivalent sayings in English, Danish, Italian, Dutch, and French. But the one I liked best was from Shakespeare’s Venus and Adonis:

      Like a red morn that ever yet betokened,
      Wreck to the seaman, tempest to the field,
      Sorrow to the shepherds, woe unto the birds,
      Gusts and foul flaws to herdmen and to herds.

    • Photo: Paul Coxon

      Paul Coxon answered on 17 Mar 2014:

      The sky appears red during sunsets because the sun is lower in the sky, and the sunlight has to travel through a larger proportion of the atmosphere to reach our eyes. This means the blue portion of the spectrum is mostly scattered out of the way by particles/specks of dust in the atmosphere leaving just the red portion remaining.

      Sky colour is linked to weather in the UK because of our position on the Earth. We”re a small island off the western coast of continental Europe and subject to lots of varying weather conditions. Most of our weather – especially big storms – comes up from the Atlantic Ocean to our west.

      “Red sky at night, shepherds delight”
      The sun sets in the west. Looking west towards a red sunset gives us an indication of what weather is heading our way over the next day. Red sky means a region of high pressure is coming towards us – this usually means the weather will be warm and sunny.

      “Red sky in the morning, shepherds warning”
      This means a red sky appears due to the high pressure weather system having already moved over us meaning the good weather has passed, most likely making way for a low pressure region which brings wind and rain.

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