# High and low temperatures reversed on certain days
**URL:** https://boards.straightdope.com/t/high-and-low-temperatures-reversed-on-certain-days/708062
**Category:** Factual Questions
**Created:** [December 23, 2014, 9:52pm UTC](https://boards.straightdope.com/t/high-and-low-temperatures-reversed-on-certain-days/708062 "2014-12-23T21:52:16Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@boffking](https://boards.straightdope.com/u/boffking)
#### Post date: [December 23, 2014, 9:52pm UTC](https://boards.straightdope.com/t/high-and-low-temperatures-reversed-on-certain-days/708062/1 "2014-12-23T21:52:16Z")
The weather app that I use sometimes does this. Right now it says “High 35, low 40” for today. What is this about? Did some designer fail math or is there a real reason for doing this?
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### Author:  [@ftg](https://boards.straightdope.com/u/ftg)
#### Post date: [December 23, 2014, 10:13pm UTC](https://boards.straightdope.com/t/high-and-low-temperatures-reversed-on-certain-days/708062/2 "2014-12-23T22:13:58Z")
Some sources give afternoon temp and overnight temp. Usually these are in the right order but can be flipped when a front moves thru. Lazy software writers coding for processing the raw data probably made a bad assumption about afternoon = high, overnight = low…
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### Author:  [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)
#### Post date: [December 24, 2014, 12:54am UTC](https://boards.straightdope.com/t/high-and-low-temperatures-reversed-on-certain-days/708062/3 "2014-12-24T00:54:26Z")
Not necessarily lazy programmers. IIRC (couldn’t relocate an official cite though I tried) …
The US NWS definition of “high temperature” is the highest temp achieved during the sun-up portion of the calendar day. The NWS definition of “low temperature” is the coldest temperature recorded between sun-down of this calendar day and sun-up of the next calendar day.
Given those definitions, it’s completely possible for the daily “high” to be cooler than the “low.” It does require a strong frontal passage, but it happens.
Like in almost all areas of human learning, “common sense” definitions are folk approximations of the deeper scientific / engineering reality. Which simplified definitions usually break down in some corner cases. Like this one.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [December 24, 2014, 2:55am UTC](https://boards.straightdope.com/t/high-and-low-temperatures-reversed-on-certain-days/708062/4 "2014-12-24T02:55:31Z")
> [@](#):
>
> Given those definitions, it’s completely possible for the daily “high” to be cooler than the “low.” It does require a strong frontal passage, but it happens.
Not if temperature is a continuous function of time, it’s not. What’s the temperature at sunset? If it’s above the nighttime low, then the moment just before sunset would also be above the nighttime low, and hence in turn be above the supposed daytime high (which hence isn’t the daytime high after all). Likewise, if it’s below the daytime high, then it’s also below the supposed nighttime low. And if it’s in between the two, then both of these are true.
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### Author:  [@Donnerwetter](https://boards.straightdope.com/u/Donnerwetter)
#### Post date: [December 24, 2014, 9:20am UTC](https://boards.straightdope.com/t/high-and-low-temperatures-reversed-on-certain-days/708062/5 "2014-12-24T09:20:52Z")
> [@boffking](#):
>
> The weather app that I use sometimes does this. Right now it says “High 35, low 40” for today. What is this about? Did some designer fail math or is there a real reason for doing this?
I would interpret this as shorthand for: “more than 35, less than 40”, the same as saying “between 35 and 40”. Expected temperature ranges are often announced as “high 30s, low 40s”, so maybe giving a “high number” first followed by a “low number” is considered somewhat intuitive in this context.
Just a guess.
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### Author:  [@boffking](https://boards.straightdope.com/u/boffking)
#### Post date: [December 24, 2014, 4:30pm UTC](https://boards.straightdope.com/t/high-and-low-temperatures-reversed-on-certain-days/708062/6 "2014-12-24T16:30:03Z")
> [@Donnerwetter](#):
>
> I would interpret this as shorthand for: “more than 35, less than 40”, the same as saying “between 35 and 40”. Expected temperature ranges are often announced as “high 30s, low 40s”, so maybe giving a “high number” first followed by a “low number” is considered somewhat intuitive in this context.
>
> Just a guess.
The reason I was asking about this is because the high and low temperatures are supposed to be for the whole day. High is the warmest it will be, and low is the coldest it will be. (Usually)