The old saying “red sky at night, sailor’s delight; red sky in morning, sailors take warning” is often used to try to predict the weather. So does a red sky really mean a tornado is coming? Here’s a quick look at the facts.
The Short Answer
A red sky alone does not necessarily mean a tornado is imminent. However, a red sky at sunrise coupled with certain atmospheric conditions can sometimes indicate an increased threat of severe weather like tornadoes within the next 12-24 hours.
What Causes Red Skies?
Red skies are caused by the scattering of sunlight through dust particles, smoke, or moisture in the atmosphere. Here are some common causes of red skies:
- Wildfire smoke – Smoke particlesscatter red light
- Dust storms – Scatter red light forward
- High humidity – Water droplets scatter red light
- Air pollution – Pollution particles scatter red light
So a vivid red sky often means there are lots of particles in the air. Some types of particles like dust or smoke may not lead to severe weather. But high humidity in the air can be associated with storm systems that may produce tornadoes.
Morning vs Evening Red Skies
The time of day also makes a difference in interpreting a red sky:
- Morning red sky – When a red sunrise occurs, it usually means high humidity or a storm system is headed your way from the west. The red light is scattered forward through moist air. This can sometimes mean enhanced tornado conditions later that day.
- Evening red sky – A red sunset often just means nice weather is headed your way from the east. The red light is scattered towards you through dry dust particles in the atmosphere. So a red sunset doesn’t necessarily mean tornadoes are imminent.
In general, a red sky in the morning is more likely to be associated with an increased tornado threat later that day compared to an evening red sky.
Other Signs of Severe Weather
While a red sunrise can sometimes portend tornadoes, there are many other signs to look for as well. Here are some other indicators that severe thunderstorms and tornadoes may occur:
- Greenish sky – Can signify hail is possible
- Wall cloud – Rotating wall cloud may produce tornado
- Debris cloud – Tornado may be occurring if see debris kicked up
- Rumbling noises – Continuing thunder can mean powerful storm
- Funnel cloud – Tornado likely if see funnel extending to ground
- Strong winds – Sudden increase in wind speed associated with storms
So it’s important not to rely on just a red sky alone. Monitor weather alerts and radar closely and look for other visual and audible tornado indicators if threatening weather is expected.
Historic Origins of the Red Sky Saying
The popular saying “red sky at night, sailor’s delight; red sky in morning, sailor’s take warning” has been around for centuries. Here’s a look at the origins:
- Appeared in the Bible – In Matthew 16:2-3, Jesus says: “When it is evening, ye say, It will be fair weather: for the sky is red. And in the morning, It will be foul weather to day: for the sky is red and lowering.”
- Mentioned in Shakespeare’s Venus and Adonis (1593): “Like a red morn that ever yet betokened, Wreck to the seaman, tempest to the field, Sorrow to shepherds, woe unto the birds, Gusts and foul flaws to herdmen and to herds.”
- Also referenced in weather rhymes collected by Martin Ingram in 1859: “Evening red and morning grey, Sets the traveller on his way; Evening grey and morning red, Brings down rain upon his head.”
So the general association between red skies and changing weather conditions dates back centuries. Early sailors, farmers, and shepherds relied on the rhyme to help predict conditions. While not 100% accurate, it captures the general correlation between red skies and shifting weather patterns.
The Science Behind It
There are several scientific reasons why red sunrise skies can sometimes indicate an increased threat of tornadoes:
- Light scattering – Longer red wavelengths in sunlight are scattered by water droplets or dust particles in the atmosphere. This scattering process creates vivid red colors.
- Approaching weather systems – The humid, stormy conditions favorable for tornadoes can scatter red light forwards towards the viewer at sunrise.
- Instability – The mix of warm, moist air combined with atmospheric instability encourages severe thunderstorm development capable of producing tornadoes later in the day.
So in summary, the same conditions that contribute to red morning skies are also favorable for tornado formation if severe thunderstorms develop. However, many red sunrises still don’t lead to tornadoes, so other confirming factors are needed.
Studies on Red Sky Accuracy
Several studies have analyzed the accuracy of the red sky rule:
| Study | Data Source | Accuracy |
|---|---|---|
| Snider (1978) | 25 years data from St. Louis, Missouri | 57% – 64% accuracy |
| Lee (1986) | 5 years data from South Dakota | 55% – 58% accuracy |
| Kren et al. (2009) | 87 days data from Nebraska | 59.8% morning accuracy |
The studies found the red sky rule to be a bit better than a coin flip, but far from foolproof. However, accuracy was higher for red sunrise forecasts compared to red sunsets. So the old saying is on to something, particularly for red morning skies signaling potential tornadoes later that day.
Famous Examples of Red Sky Warnings
There are several notable examples of stunning red skies preceding major tornado events:
- April 14, 2012 – Bright red sunrise over Kansas and Nebraska preceded an outbreak of nearly 100 tornadoes, including an EF-4 twister.
- May 31, 2013 – Red sky at dawn in Oklahoma City area hours prior to a deadly EF-5 tornado that killed 24 people.
- April 27, 2014 – Dramatic red sunrise in Arkansas forecast major tornado outbreak with 35 twisters across the South.
- March 1, 2017 – Vivid red sky in Missouri acted as harbinger for EF-4 tornado that hit Perryville area that evening.
These events demonstrate how red sunrise skies can provide advance visual cues of significant tornado risk later that same day in some cases.
Conclusion
In summary, while a red sky alone does not guarantee a tornado is coming, an ominous-looking red sunrise can sometimes act as a warning sign for potential tornado conditions later that day. This is especially true if there are other indicators like high humidity, stormy forecast, or spinning wall clouds. The old saying remains a useful general rule, but should be combined with modern weather monitoring and warnings to assess tornado risk most accurately. Heeding potential red sky warnings by taking safety precautions is always a wise idea.
