The Reason Why The Sky is Red at Night When It’s Going to Rain


Last Updated on 2020-12-02 , 7:28 pm

There is a running inside joke among Malaysians and Singaporeans that we , too, have four seasons in our tropical climate.

Instead of the usual four seasons of spring, summer, autumn and winter, our four seasons consists of rainy, sunny, cloudy and hazy.

We have grown used to these weather conditions and adapted ourselves accordingly. Sometimes, we can be the meteorologists and we’ll guess (correctly) the weather on the next day.

A weather forecaster in action

When we spot a red sky in the late evening or night, there is bound to be that one person who say that it will rain sometime later in the night; or perhaps that person is you.

Ever wondered whether is this just some old grandmother story or is it actually based on facts?

Here’s the scientific explanation behind it.

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Scientific explanation (sort of)

Now this is going to be slightly chim so bear with me.

The red skies appear based on the reflection of light and how it bounces around in the atmosphere.

We all know that heavy, ominous dark clouds gathering on the horizons during the daytime mean rain but we can rarely see high clouds during night time as the sky has already turned into a sea of darkness.

Reflection of city lights

Nevertheless, what we have in these modern times is the lights from the city.


City lights glow bright and strong, seemingly even more so when they are reflected from the low clouds in the sky.

These low rain clouds can hover at just a few hundred feet above ground, allowing the glow from the metropolis to light up the sky. Thus, you are able to spot the low clouds and sky.

Why red?

The colour of the sky is caused by the reflected city lights and appears red even though there doesn’t seem to be a strong red tinge in the lights of the city.

A theory suggests that this is because the blue and indigo components of light are minimized during the reflection and also its passage through the atmosphere.

This leaves behind the orange and red components which are why we perceive the sky as red. After all, most of our street lights are orange, right?

Of course, when the downpour starts, the reddishness dims and we are not able to see the reflected light as clearly.

In others word, to put it simply, it’s red not because the sky’s angry: it’s red because of the reflection from our city lights.

Interesting, no?

Image: Rebeccakarenza /