What are hailstones and how are they made?

What are hailstones and how are they made?

The simple science twins are back to answer more of your questions; this one is all about hailstones and it comes in from five year old Matthew who can sometimes be found over on Office Mum’s blog. Matthew would like to know…

What are hailstones and how are they made?


What are hailstones?

Hailstones are small lumps of ice that form in the clouds and fall to the ground when their size reaches 5 mm in diameter, or larger.

They begin as water droplets that freeze in the clouds.

How are they made?

Hailstones are made in certain kinds of clouds, called CULUMONIMBUS. These are thunder clouds and if the cloud is large enough and the winds are strong enough, hailstones can be formed.

Firstly, the cloud contains tiny droplets of water. Under the right conditions, these droplets are blow to the top of the cloud by strong winds, called UP-DRAFTS. The temperatures at the top of the cloud are a lot lower than at the bottom so the water droplets freeze rapidly. Then they can be caught by winds, called DOWN-DRAFTS that carry the frozen droplet back down to the lower part of the cloud. It gets lifted again, by another up-draft and combines with another droplet of water, which freezes, forming a larger lump of ice.

Every time it travels up to the top of the cloud it merges with more droplets and gets larger, freezing in layers, until eventually it is too big and heavy to stay in the cloud and it falls to the ground as hail.

Hailstones usually fall once they are larger than 5 mm in diameter.

The size of the hailstones depends on the up-drafts and down-drafts and the general weather conditions. When the up-drafts become stronger the thunder clouds grow taller, allowing the droplets to be carried higher into colder temperatures. This usually leads to larger hailstones.

The largest hailstone ever recorded was 20 cm in diameter and weighed 0.88 kg. It fell in Vivian, South Dakota, USA on July 23rd, 2010.

What is the difference between snow and hailstones?

Hailstones are made up of layers of frozen ice whereas snow is a symmetrical crystal of ice, usually a snowflake.

Hailstones are much heavier than snowflakes and fall at a greater speed.

Snow is usually formed during the colder months of the year, in Winter or Spring whereas hailstones can be made at any time of the year. That is why we sometimes get them in the Summer months.


Thanks so much to Matthew for sending in this great question. If you have a question that you’d like the simple science twins to answer, send it in to me at drhowsciencewows@gmail.com or leave it in the comments below.


Mystery Creature – June 2017

Mystery Creature – June 2017

We’re heading to the deep blue sea for this month’s Mystery Creature. Not the prettiest looking animal, and it certainly has some very unusual features; it’s a bit of a living fossil, do you know what it is?

Image credit:By Peter Southwood (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

As usual, feel free to ask questions, look for clues or leave comments below. Remember to check back at the end of the month for the big reveal.



Mystery creature revealed – the Resplendent Quetzal

Mystery creature revealed – the Resplendent Quetzal

How did you do with last month’s Mystery Creature? I know I am a bit (very) late posting this reveal, I’ve been busy in the background, despite the quiet status of the blog of late.

Rather than a long ramble, back to the task at hand, the reveal… last months Mystery Creature was the aptly named Resplendent Quetzal!

Image credit:By Supreet Sahoo - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=58173977

The Resplendent Quetzal

The Resplendent Quetzal (Pharomachrus mocinno) belongs to the Trogon family. There are two recognised subspecies… P. m. mocinno and P. m. costaricensis.

Here are five more facts about these amazing birds

1. These beautiful birds are found in mountainous rainforests of Central America. Their habitat stretches from Southern Mexico to Western Panama. They are particularly partial to cloud forests, hanging out near the top of the tall forest canopies, blending in with all the natural colour around them.

2. Resplendent Quetzal are not strong flyers. They prefer to take short flights or hop among the branches. They have an interesting toe configurations, with two toes facing forwards, two facing backwards. This facilitates good gripping in the branches in the forest canopies they prefer. They are not so good for walking though, which is why they are very rarely spotted down on the ground.

3. Resplendent Quetzal were much revered by ancient civilisations such as the Aztecs and the Mayans; They were considered sacred birds, not surprisingly, as they really do have a beautiful plumage of iridescent green/blue feathers with a red breasted front. Males tend to be a little more colourful than females. The males grow two very long tail feathers on reaching sexual maturity. These feathers can grow up to a metre in length and often featured in royal costume among the Aztecs and the Mayan people.

4. It is the national bird of Guatemala, visible on their flag and coat of arms. In fact their currency is called Quetzal too.

Image source: wiki commons

5. Male Resplendent Quetzal are not thought to reach sexual maturity for many years. This is when they grow those two impressive tail features, hoping to show themselves off and attract a mate. Males will also perform fairly lavish displays and dances, which an interested female may mimic. Mating pairs dig a nest out of rotten tree stumps or branches and both parents are involved in incubating the brood of two to three pale blue eggs that the female lays. The chicks are often ready to fly within three weeks of hatching but it can take a few months before they fully fly the nest. The mother will then be finished with her duty of care but it has been reported that the father will still supplement their diets for a year or more.

I’m sure you will agree, a very interesting and beautiful bird. Check back tomorrow for this month’s Mystery Creature, see if you can guess what it is.