Bureau of Meteorology


The BOM Blog gives you the background and insider info on weather, climate, oceans, water and space weather—as well as the latest on the work of the Bureau.


We welcome participation in the comments section of our blog; however, we are not able to respond to all comments and questions and your comments may take a little time to appear. The blog is monitored from 9 am to 5 pm Monday–Friday.

Our community includes people of all ages and backgrounds and we want this to be a safe and respectful environment for all. To keep the discussion interesting and relevant, please:

  • respect other people and their opinions;
  • keep your comments on topic and succinct;
  • say why you disagree or agree with someone;
  • comment constructively—in a way that adds value to the discussion.

When commenting, please don't:

  • make defamatory, libellous, false or misleading comments;
  • use obscene, insulting, racist, sexist or otherwise discriminatory or offensive language;
  • post personal information about yourself or others, such as private addresses or phone numbers;
  • promote commercial interests;
  • violate the intellectual property rights of others;
  • violate any laws or regulations;
  • provoke others, distort facts or misrepresent the views of others; or
  • post multiple versions of the same view or make excessive postings on a particular issue.

We won’t publish comments that are not in line with these standards. Blocking/removal of content or banning of users is at our discretion.

There is no endorsement, implied or otherwise, by the Bureau of any material in the comments section. Users are fully responsible for the content they submit.

Commenting is available via a Facebook plugin, which can only be accessed by those with Facebook accounts.

You can contact us at bomblog@bom.gov.au.

Copyright | Disclaimer | Privacy


Contact our social media team at socialmedia@bom.gov.au

AskBOM: What is a thunderstorm?

AskBOM: What is a thunderstorm?

Thunderstorms are associated with very tall clouds called cumulonimbus that produce turbulence, lightning and thunder. So what causes them, and what's really going on up there?

How are thunderstorms formed?

Thunderstorms need three ingredients to form:

  1. Moisture—humid air carrying a lot of water vapour, which can be visible as low clouds or haziness in the morning or many small cumulus clouds later in the day.
  2. A lifting mechanism—a force that makes the moist air rise rapidly, such as:
    • an advancing cold front, where colder, denser air pushes under the warmer air ahead of it, lifting it;
    • orographic lift, when air is forced upwards as it moves over rising terrain, such as mountains;
    • sea breeze convergence, as cooler wind from the sea moves inland, lifting the warmer air there; or
    • thermal lift, as the day’s sun heats air near the earth, causing it to rise.
  3. Atmospheric instability—as warm air rises into cooler air above, it will keep rising as long as it is warmer than its surroundings. If the air rises far enough, the moisture in it condenses and forms cloud.

When the atmosphere is particularly unstable, and/or additional energy is drawn in from surrounding winds, thunderstorms can become more intense.

The life of a thunderstorm

A typical thunderstorm lasts for about half an hour to an hour, and goes through three stages:

  1. Towering cumulus stage, where the entire cloud consists of updraft (air rising).

Towering cumulus

  1. Mature stage, when the thundercloud is at its largest and most organised. In addition to the updraft, there's also a downdraft (air descending) where most of the heavy rain occurs. The cloud now produces thunder and lightning, and takes on an ‘anvil’ shape as air at the top can no longer rise any further, so it spreads out sideways.

Mature thunderstorm

  1. Dissipating stage, when the energy supply to the storm is coming to an end, the updraft and downdraft are dying, and the cloud dissolves.

Dissipating thunderstorm

When do thunderstorms strike?

Most thunderstorms in Australia form during the warm season—September to March—when the sun provides a stronger thermal lifting mechanism. We can also experience cool-season thunderstorms, particularly if other lifting mechanisms are strong: Severe winter storms linked to cold fronts are common in the southwest of Western Australia and the southeast of South Australia.

Can we tell when thunderstorms will happen?

We can forecast broadly where and when thunderstorms are likely to form, but not exactly. This is because very small differences in temperature and moisture make the difference between a large thunderstorm event and no thunderstorm at all.

If thunderstorms are forecast for your area, keep an eye on www.bom.gov.au for the latest warnings. You can also use our rain radar web pages to see whether storms are headed your way, or switch the satellite imagery at satview.bom.gov.au to ‘Infrared + Zehr’ to highlight deep convection—generally associated with thunderstorms and cyclones.

Know your weather. Know your risk.

Click here to subscribe to this blog

Comment. Tell us what you think of this article.

Share. Tell others.