2487: Danger Mnemonic

Explain xkcd: It's 'cause you're dumb.
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Danger Mnemonic
It's definitely not the time to try drinking beer before liquor.
Title text: It's definitely not the time to try drinking beer before liquor.


The teacher Miss Lenhart warns two small kids using a danger mnemonic.

However, this is actually a mash-up of three different common danger mnemonics, each of which warn about different hazards.

  • Red touches black, that's a friend of Jack; red touches yellow, you're a dead fellow.

This mnemonic is intended to help recognize venomous coral snakes, which have brightly colored stripes. Some nonvenomous king snake species have similar striped colors, but in different patterns. NOTE THAT THIS MNEMONIC IS NOT ACCURATE, ESPECIALLY OUTSIDE THE EASTERN UNITED STATES WHERE IT WAS ORIGINALLY CREATED; many species of coral snake have black stripes touching red stripes, and if the snake has atypical coloration, then the rhyme may still lead to misidentification even in the right region. The safest course of action is to avoid any snake with the warning colors of red, yellow/white, and black stripes. Another corruption of the same warning features in 1604: Snakes.

  • Leaves of three, leave them be; berries white, poisonous sight. (Alternatively, "berries white, run in fright" or "hide from sight.")

This mnemonic is used to identify poison ivy and poison oak throughout much of North America. These plants both produce an oily surface resin called urushiol, which causes an allergic reaction in the majority of people. Touching either plant can result in contact dermatitis, which can be severely itchy or painful. If burned, the urushiol can be inhaled, causing lung irritation. While rarely serious, these reactions are often severely unpleasant and can last for weeks, so avoiding the plants is well advised. Both plants generally grow three leaves at the end of each branch, and grow berries that turn white when ripe. The mnemonic helps in remembering this characteristic to distinguish them from similar-looking but harmless vines. See 443: Know Your Vines.

  • Red sky at night, sailor's delight; red sky in the morning, sailors take warning.

This mnemonic predicts bad/good weather conditions based on a particularly red sunrise/sunset. It is predictive at middle latitudes where the prevailing winds go from west to east. Regions of higher air pressure will cause a particularly red sky at sunrise/sunset, so a red sky in the evening indicates a high pressure system is coming in from the west with its calmer weather, while a red sky in the morning indicates a low pressure front coming in (usually with rain and rougher weather). In some countries (such as the United Kingdom), the saying mentions shepherds rather than sailors. Randall actually wrote a newspaper article explaining this phenomenon.

Combining all three sayings sounds particularly ominous. It implies that a person is involved with a situation simultaneously involving coral snakes, poison ivy, and potentially nasty weather. In such a case, Miss Lenhart advises the children to "just get out of there", implying that the situation is too dangerous to try to deal with.

The title text refers to another mnemonic: 'Beer before liquor, never been sicker; liquor before beer, you're in the clear.' Unlike the first three mnemonics, which are genuinely useful for avoiding danger, this one is largely a myth, as the order in which you drink alcohol is unlikely to impact how sick you become. However, whether the mnemonic is true or not, testing it would involve multiple drinks of alcohol, which would be ill-advised when facing a dangerous situation, particularly one as bizarre and complex as implied in this strip.

See also 2422: Vaccine Ordering for the previous time xkcd referenced the latter mnemonic.

See also 2038: Hazard Symbol for another combination of danger warnings.


[Miss Lenhart is holding a finger up in front of two children: a boy with spiky hair and Jill.]
Miss Lenhart: Now, remember:
Miss Lenhart: If red touches yellow amid leaves of three under a red sky at morning,
Miss Lenhart: You should probably just get out of there.

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1) Strangely, I find even the established motherWiki page for the Red Sky motto to be a little short of full explanation. It could do with a diagram to demonstrate how line-of-sight extends one's view beyond the horizon and above surface effects to reveal the nature of the oncoming atmosphere, either imminent (upwind) or historic (downwind, with the implication of an oscillation in the other direction). But, not only that, a sky clear enough to give a good direct red-sky in the Sun's rising/setting direction also will allow Earth-skimming sunlight to red-illuminate the presence of clouds in the opposite direction (with the greater guarantee of 'weather system opposites' east-to-west), enhancing the 'forecast' even further and before/after rising/setting of the Sun as well. Not something to add to the Explanation, but fun to realise. 08:50, 10 July 2021 (UTC)

2) Perhaps don't use a web link to wikipedia when you can use a much more elegant wikilink..? 08:50, 10 July 2021 (UTC)

3) The (probably as apocryphal?) rhyme here is "Beer before wine and you'll feel fine; wine before beer and you'll feel queer", so I leave it up to you to work out what this means for how to ultimately mix your Chateau-Whatever and your no-'e' whisky. ;) 08:50, 10 July 2021 (UTC)

So if you combine the two aphorisms, the best order is liquor->beer->wine? I don't drink, so I can't attest to the truth of any of these. Barmar (talk) 12:03, 10 July 2021 (UTC)
That's if it's not like Rock-Paper-Scissors.. :p 10:29, 11 July 2021 (UTC)

I don't think the title text is warning against getting drunk, just the particular order of drinks that the old saying warns against. She's already told the kids to "get out of there", you don't want to get sick and stop to vomit. Barmar (talk) 12:08, 10 July 2021 (UTC)

Do you reckon this is a reference to the current wildfires ... three x dangerous but the colours of red and yellow and a mention of a nature setting ... Boatster (talk) 02:00, 11 July 2021 (UTC)

In the UK I've never heard the first two of these mnemonics- we don't have poison ivy and our only venomous snake is the adder, which has zig-zag markings. And the weather warning is usually "Red sky at night, shepherd's delight, red sky in the morning, shepherd's warning. -- 07:33, 12 July 2021 (UTC)

Watch A Perfect Storm to see why sailors should be very concerned with upcoming weather. Barmar (talk) 19:49, 12 July 2021 (UTC)
"the order in which you drink alcohol is unlikely to impact how sick you become"

Not directly, but it can easily affect how much you ultimately drink! The reasons you'll get "sicker" drinking beer before liquor are that, after consuming a few drinks (of either type), the alcohol will have numbed your mouth a bit, so that a strong drink no longer tastes as strong, and also that your judgement will have become impaired, making it easier to accidentally overindulge. Now, consider the fact that beer has a much lower concentration of alcohol than liquor has. Therefore, if you start off with beer, and then switch to liquor, you could very easily consume far too much alcohol, whereas if you start off with liquor, and then switch to beer, it becomes much more difficult (though, to be fair, certainly not impossible) to consume significant quantities rapidly, because you'll tend to get physically full after a few beers. Even if you don't have the presence of mind to consciously control your intake, your subconscious mind will stop you from consuming anything once your stomach is completely full.

Don't believe me? Try it — pour yourself a big glass of water and see how quickly you can drink it. Repeat until you feel "full". Then fill that big glass up one more time, and notice how long it takes you to finish it. You'll have a hard time taking more than a small sip at once; your body just won't let you do more. Dansiman (talk) 17:40, 13 July 2021 (UTC)

Randell's actally explained the "red sky at night" saying in his book "How Too" ;) Apollo11 (talk) 22:42, 19 March 2024 (UTC)