Is the Equinox causing this heat wave?

Is the Equinox causing this heat wave?

‘Is it just me or is this place melting?’ That’s probably most of Kenyan residents are asking. Esp in Nairobi and Coast Counties. It feels like the sun has just updated its drivers and the new update brings with it more heat. What might be causing all this?

Yesterday The Star reported that Coast residents are urged to stay indoors from 12 pm to 3 pm due to a temperature soar that was caused by the ‘equinox phenomenon’ that would affect the county for the next five days. They then followed with advice like regularly checking your blood pressure as frequent (sic) as possible and substituting meat intake with fruits and vegetables. The Star editors would have told that this message was a hoax just from the circular’s title ‘No Joke’. Or from the fact that it was not signed. Or because it had no dates. Or from Googling the message and seeing that the same exact message was used in other countries like Singapore. But I will ignore all that and just use this opportunity to talk about the equinox.

Now, I am not refuting that there’s a heat wave going around. In fact, this February has gone on record as being the hottest month in recorded history. My issue is the belief that all this heat is because of the equinox.

So what exactly the equinox? The equinox is a phenomenon that occurs when the plane of Earth’s equator passes through the center of the Sun ie, the sun is directly overhead the equator. See, the earth is a rotating spheroid that spins on an axis that is tilted at around 23.4°. This axis also rotates, and twice a year, it happens that the axis is upright and the sun hits the earth equally both in the upper and lower hemispheres.



During the equinox, the days and nights are of 12 hour lengths in both the Northern and Southern Hemispheres. This event occurs around Mar 20th (vernal aka spring aka northward Equinox) and around September 23rd (autumnal aka September aka southward equinox).  The equinox marks changes in seasons; the northward equinox, for instance, marks the start of spring in the Northern Hemisphere and the start of autumn in the Southern Hemisphere.

This year the equinox started on March 20th at 7.30 EAT – the earliest since 1896 . But the one in 2020 will happen even earlier. And the one in 2100 even earlier still.

An interesting thing about the equinox is that despite the term equinox (from Latin meaning equal night) meaning equal days and night, the days and nights are technically not exactly equal during the equinox. The days are usually longer by a few minutes. This disparity is mainly due to two things: The angular size of the sun and atmospheric refraction.

‘1.  from the Earth, the Sun appears as a disc rather than a point of light, so when the centre of the Sun is below the horizon, its upper edge is visible. Sunrise, which begins daytime, occurs when the top of the Sun’s disk rises above the eastern horizon. At that instant, the disk’s center is still below the horizon.

2.  Earth’s atmosphere refracts sunlight. As a result, an observer sees daylight before the top of the Sun’s disk rises above the horizon. Even when the upper limb of the Sun is 0.4 degrees[citation needed] below the horizon, its rays curve over the horizon to the ground.’ – Wikipedia

Therefore, due to the disc shape and wave refraction, days and night are not exactly equal during the equinox. Exactly 12 hours of light and 12 hours of darkness happens a few days before the March equinox (and after the September equinox) depending on your location. At the equator, the days are always longer than the night.

Approx date of “Equal Day & Night”
Latitude          March     September
60° North Mar 18 Sep 25
55° North Mar 17 Sep 25
50° North Mar 17 Sep 25
45° North Mar 17 Sep 25
40° North Mar 17 Sep 26
35° North Mar 16 Sep 26
30° North Mar 16 Sep 27
25° North Mar 15 Sep 27
20° North Mar 14 Sep 28
15° North Mar 12 Sep 30
10° North Mar 8 Oct 4
5° North Feb 24 Oct 17
Equator No equal day and night
5° South Apr 14 Aug 29
10° South Apr 1 Sep 10
15° South Mar 28 Sep 14
20° South Mar 26 Sep 16
25° South Mar 25 Sep 17
30° South Mar 24 Sep 18
35° South Mar 24 Sep 19
40° South Mar 23 Sep 19
45° South Mar 23 Sep 19
50° South Mar 23 Sep 20
55° South Mar 23 Sep 20
60° South Mar 22 Sep 20

There are a lot of customs in different regions regarding the equinox. Like the Chinese belief that the equinox is the only day that you can balance an egg on its end. And now Kenya is on its way to believing that equinox causes heat waves.

The equinox does not mean more heat in the way ‘the circular’ put it. It just happens for one day in March (and another in Sept) and it actually does not affect us Kenyans much cos we are close to the equator. Our days and nights are more or less equal.

However, the source of heat wave still needs addressing. The cause has been attributed to climate change. The climate has been getting harsher over the years although some still do not agree on whether it’s human induced change. What however we can all agree it on the harshness. It would be interesting to see Kenya Meteorological Service publicize the weather trends. Is this the hottest March in Nairobi for the last decade? Is this related to the El Nino? At least the meteorologists trashed the ‘No Joke’ circular however. Unfortunately, some took it to mean that the scientists are acknowledging the blistering weather.

In conclusion, no one can dispute this heat wave. What we are disputing is that it is being caused by the equinox. Do you still think it’s being caused by the equinox, let us know why.

Read more about the equinox

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The RocKe Scientist is an award winning earth science platform based in Kenya.

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