• Question: why do clouds turn grey when it is about to rain?

    Asked by syria12345 to Laura, Lily, Mark, Paul, Sarah on 21 Jun 2010 in Categories: .
    • Photo: Sarah Bardsley

      Sarah Bardsley answered on 21 Jun 2010:

      Ah ha my boyfriend studied meteorology at uni! I’ve just asked him and its because these clouds are thicker because they have more water in them, therefore they block the light and appear greyer.

    • Photo: Lily Asquith

      Lily Asquith answered on 21 Jun 2010:

      Hmm. Well, white objects are white because all the light is reflected off them.

      And white objects look grey when they are in shadow, meaning that the object is still reflecting all wavelengths of light, but the intensity (amount) of light is lower.

      So I guess the cloud is in it’s own shadow, because it is full of rain and therefore it is more dense.

      This might not be right!

    • Photo: Laura Maliszewski

      Laura Maliszewski answered on 21 Jun 2010:

      Clouds don’t have their own color, they’re only water vapor. This is why they look many colors during sunset, they’re reflecting the light of the sun.

      When a cloud is very full of moisture just before raining, it’s so dense that it blocks light instead of reflecting it, looking dark.

    • Photo: Mark Roberts

      Mark Roberts answered on 21 Jun 2010:

      I’ll admit to having to look this up

      but they look grey due to how the water vapour interacts with the light shining through it – the water droplets only allow light that appears to us as grey through. If you were to fly to the top of the storm clouds, they would look white because the light is reflected back to you – rather than the light that is let through

      Does that answer your qu?

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