• Question: what exactly causes rain, hail and snow?

    Asked by Lillian to Hugh, Ed, Dave on 12 Mar 2015.
    • Photo: Dave Bond

      Dave Bond answered on 12 Mar 2015:

      Hi Lillian,

      Well water vapour is held in the air and depending on air temperatures it falls as either rain, snow or hail. Snow has to be not too cold else the ice forms too quickly and does not “fluff” out into a snow flake. The ice crystal does not grow as big forming hail. Hail is also a frozen droplett of water, unlike snow where the water crystalizes out of the vapour.

      Not my piticular area of knowledge so others please correct me.

    • Photo: Ed Rial

      Ed Rial answered on 13 Mar 2015:

      Hi Lillian

      Rain, hail and snow form part of the Water Cycle, and they all start their lives in clouds.

      The sun heats the seas and the earth and evaporates water into the air, as the water rises through the air (water vapour is lighter than air) it rises to parts of the atmosphere that are colder. Cold air can’t hold so much water vapour, so the water forms first clouds and then either water drops that fall as rain if the temperature is above freezing, or ice crystals that fall as snow if the temperature is below freezing.

      Hail is different in that it starts life in the same way as rain, but if it falls during a thunderstorm where there is a strong upwards gust of wind the rain can be driven up higher into the atmosphere where the temperature is below freezing. Because the water is already in the droplet it forms a little ball of ice (a hailstone) rather than an ice crystal (snow flake).

      It then falls to the ground as hail.

      I had to look up how hail was made – but I thought that was very interesting!

    • Photo: Hugh Harvey

      Hugh Harvey answered on 13 Mar 2015:

      Rain, hail and snow are different forms of water at different temperatures, depending on how high up in the atmopshere they fall from. The higher you go, the colder it is!

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