# If the Earth had 48 hour days, how much would the temperature drop at night and raise in the day?

I'm building a world that's essentially identical to Earth, except that it spins slower, making the days about 48 hours long. I'd like to know what the average temperature drop at night would be, and what the average raise in temperature during the days would be. I'm chiefly interested in data for the temperate regions (U.S. and Europe latitudinal areas).

• Interesting question, there have been some similar queries in the past but none that have quantified the variation. I'm looking forward to a good answer. However, an answer covering every latitude, altitude, climate zone and season would be book length, which means that the question is likely to be closed for requiring more focus, so you may need to focus on a particular climatic zone in a particular latitude and then look at follow-up questions for other zones of interest. Commented Oct 5, 2023 at 21:58
• Thanks for the advice, I'll make some changes. Also, my question does specify that I'd like averages, which could be found for large areas such as ranges of latitude. Commented Oct 5, 2023 at 23:19
• Well, don't pick the Midwest. If the jet stream is coming from Texas, it doesn't get cold at night in Chicago, nor would we notice any difference from any given day where we sometimes experience all four seasons by lunch. "lots of wind" (and what might happen to your climate zones, but not much about temperature) : worldbuilding.stackexchange.com/a/18795/799 Commented Oct 6, 2023 at 0:50
• I agree with @KerrAvon2055. This is a good question and asking for an average temperature shift is a great start. I can easily imagine temperatures getting whomping hot and ridiculously cold, which would lead to a substantial increase in wind. It might take 3-5 questions (each building on the previous) to get a reasonable set of details, but it'll be interesting.
– JBH
Commented Oct 6, 2023 at 2:35
• "A planet's sidereal day is of importance primarily for the temperature variances on the surface. A pleasant average temperature, on paper, can in fact be a mean value calculated from the scorching day's and freezing night's respective temperature. Vast oceans and an atmosphere will of course mitigate these effects, but on a planet that rotates very slowly around its own axis (where one night might last several Earth months, for example) the variations would be quite noticeable and therefore sidereal day should probably be included when a habitability index is calculated." Commented Oct 8, 2023 at 21:44

## 1 Answer

Worldbuildingpasta I know this ought to be a comment(ish) being a long time lurker on stack exchange in general, but you should check out worldbuildingpastas climate models. As this cannot be a comment however, I'll simply tell you the results using it as my source.

(Second draft) Two things would occur,fist off, the first being that day and night temprature would vary, but this would be mitigated, to an extent due to an a localclimate that is increasingly closer to the average climate. Such a planet would have a larger and slight colder equatorial zone, with temperatures becoming increasingly uniform across the planet up to a day length of roughly 360 hours, the local climate, and temperature of regions on the planet would become increasingly closer to the average temprature of the planet. This means as a result that while colder than most nights on earth, earth like plants and animals would have no trouble surviving on such a planet, with a steady temprature being present on the coasts,and rainforest, with the more extreme reigons ending up experiencing an extra 5 degrees celsius and less being closer to 2.5 celsius of temprature varation,so behaps slightly less in the way of arable areas.

• You cannot be serious when you say that the local climate would become closer to the average climate. As the daily cycle becomes longer, the difference between maximum daily temperature and minimum temperature would naturally increase, and the difference between continental climates and oceanic climates will also increase. Commented Oct 6, 2023 at 22:38
• Again, I'm citing the model. Sometimes the climate behaves counterintuitively. You can come up with a crap ton of examples. The atmosphere of the earth for one gets colder, warmer than colder again with altitude. They're complex systems, and intuition alone can only get you so far. Commented Oct 6, 2023 at 22:45
• The answer is not citing anything. Commented Oct 6, 2023 at 22:46
• Nice link, but it seems that it does not agree with you because it says: "longer days allow for both more heating during daylight and more cooling at night, creating greater extremes of temperature each day". About 120-hour day it says: "This is now a more substantially different climate, with climates not just shifted but in some ways rearranged." Commented Oct 6, 2023 at 23:13
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– Community Bot
Commented Oct 7, 2023 at 0:18