Red Sky at Morning, Hikers Take Warning

Having grown up along the coast of Maine, there was a saying instilled in me by my parents every time I was planning to go outside for an extended period of time: “Red sky at morning, sailors take warning. Red sky at night, sailors’ delight.”

This got me in the habit of looking out at the sunrise and sunset every day with the phrase repeating in the back of my mind. It was my parents’ way of getting me to pay attention to the weather when I was going out, and to take appropriate clothing or be home before a storm might roll in.

Working for Mount Washington Observatory, I have heard a similar phrase repeated to me by hikers that I have encountered on the summit while out taking weather observations. It however switches out the “sailors” for “hikers” in the rhyme.

Sunrise over undercast on Feb. 14, 2022.

While many have undoubtedly heard a variation of this rhyme before, where does it come from? And is there any scientific backing to this phenomenon? The history of this phrase dates back to at least the 1st century AD, and it was cited in the New Testament showing prevailing knowledge of the seafaring people of the time. Shakespeare also used it in his play Venus and Adonis. It has been rewritten and adapted countless times since then.

As for scientific backing, the phrase does explain in some basic terms phenomena that we observe with the weather both at sea and in the White Mountains. To understand how this lore can be used to predict the weather, we must first look at colors in the sky and the prevailing winds.

The Tip Top House is shown with newly fallen snow at sunset on June 19, 2022.

In the mid-latitudes, the prevailing winds are Westerlies, meaning the wind is from the west and storm systems move west to east. A storm system typically has high atmospheric moisture and dust content, which can scatter light coming in from the sun. During the sunrise and sunset, the light is projected through the troposphere, which is the densest part of the atmosphere. This is additionally where all of the Earth’s weather is confined.

A deep red sunrise or sunset suggests that the atmospheric particles are concentrated enough that they are scattering shorter wavelengths of light and only permitting the longest wavelengths, red, to pass through. As areas of low pressure deepen, they tend to collect more particles, leading to the development of clouds and storms, whereas building high pressure leads to fair-weather skies and clearing weather patterns.

Sunset from the observation deck on Aug. 13, 2022.

So how does this apply to the rhyme? In a general sense, in order to see a sunrise or sunset, the region is typically under the influence of high pressure as the skies are clear enough to see the sun. Knowing that, let’s look at the first part – red sky at morning, hikers take warning. We know that the red color is caused by the scattering of light as it passes through the atmosphere, as the sun rises from the east. This light is scattered off the approaching clouds and the increasing suspended particles as low pressure and storm systems move in.

Now for the second part – red sky at night, hikers’ delight. The same principles of light diffraction apply. However, since the sun is setting in the west, the departing clouds are now illuminated, signaling high pressure to follow.

While this does provide a natural warning, if you are planning on hiking in the White Mountains, it is still always best to check out our Higher Summits Forecast ahead of your trip.

Nimbus looking out at sunset on Aug. 14, 2022.

Hayden Pearson, Weather Observer & Research Specialist

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