<p>If you consider a closed system, this will be true, as dewpoint is related to the absolute moisture which is not a function of temperature.  However, as Fred's answer demonstrates, the atmosphere is not a closed system.  Even devoid of fronts and severe weather there are still pressure gradients which result in wind.  Wind advects moisture and so if there is wind the moisture (dew point) can change.  </p>

<p>Furthermore if we consider surface fluxes that statement becomes even less true.  With no advection if we have vegetation or standing water on the surface we can increase the dew point just through evapotranspiration. </p>

CC BY-SA 3.0
2015-08-12T14:26:38.770Z
2015-08-12T14:26:38.770Z
casey
<p>From a review of weather observations, that statement is false.</p>

<p>Below are  the synoptic weather maps for Australia for 11 August 2015 and  <a href="http://www.bom.gov.au/australia/charts/synoptic_col.shtml" rel="nofollow noreferrer">12 August 2015</a>. There are no weather fronts, or adverse weather in the western two-thirds of the continent.</p>

<p><a href="https://i.sstatic.net/3BHgI.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/3BHgI.png" alt="Aus synopic map 20150811"></a></p>

<p><a href="https://i.sstatic.net/6Tjx3.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/6Tjx3.png" alt="enter image description here"></a></p>

<p>Alice Springs (lat:-23.8, long: 133.89) is in the centre of the continent. It's <a href="http://www.bom.gov.au/products/IDD60801/IDD60801.94326.shtml" rel="nofollow noreferrer">weather observations</a> for 11 August 2015 reveal the temperature ranged between $5.8$ $^oC$ and $26.0$ $^oC$ and the dew point  range was between $-18.8$ $^oC$ and $-2.5$ $^oC$.</p>

<p>Similarly for <a href="http://www.bom.gov.au/products/IDD60901/IDD60901.94120.shtml" rel="nofollow noreferrer">Darwin</a> (lat: -12.42, long: 130.89), which is located on the coast in the sub tropics, in the central north of the country, the temperature range for 11 August 2015 was $19.7$ $^oC$ to $30.1$ $^oC$, while the dew point range was $15.4$ $^oC$ to $19.8$ $^oC$.</p>

<p><a href="http://www.bom.gov.au/products/IDW60901/IDW60901.94610.shtml" rel="nofollow noreferrer">Perth</a> (lat: -31.93, long: 115.98), on the southern western coast has a temperate Mediterranean climate. It's temperature range was $10.2$ $^oC$ to $17.6$ $^oC$ and the dew point range was $5.7$ $^oC$ to $11.7$ $^oC$.</p>

<p><a href="http://www.bom.gov.au/products/IDS60901/IDS60901.94672.shtml" rel="nofollow noreferrer">Adelaide</a> (lat: -34.95, long: 138.52), on the southern coast, in the centre region , also has a temperate climate and its temperature ranged from $7.6$ $^oC$ to $15.4$ $^oC$ and the dew point range was $-0.3$ $^oC$ to $8.5$ $^oC$.</p>

<p>Lastly, <a href="http://www.bom.gov.au/products/IDQ60901/IDQ60901.94578.shtml" rel="nofollow noreferrer">Brisbane</a> (lat: -27.39, long: 153.13) which is on the east coast  had temperatures between $8.2$ $^oC$ and $21.9$ $^oC$ and the dew point varied between $6.9$ $^oC$ and $15.8$ $^oC$.</p>

<p>All these weather observations show significant variance in the dew point for these locations given the respective temperature ranges and the lack of weather fronts and adverse weather systems.</p>

CC BY-SA 3.0
2015-08-12T03:55:33.163Z
2015-08-12T03:55:33.163Z
Fred
<p>Is this true?
"If there are no weather front or severe weather systems, then the dew point within a single day is fairly constant, no matter how large the day/night temperature variation."</p>

CC BY-SA 3.0
2015-08-12T01:46:34.147Z
Where did you find that statement? reference? link?
arkaia
<meteorology><temperature>
Dew point variation in a day
Nissa
# Dew point variation in a day

(Asked by: username_0 on 2015-08-12)

Is this true?
"If there are no weather front or severe weather systems, then the dew point within a single day is fairly constant, no matter how large the day/night temperature variation."

**Tags:** meteorology, temperature

> **Comments:**
> **username_1**: Where did you find that statement? reference? link?  

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## 2 answers

### Answer by username_2 on 2015-08-12. Score: 0 | Accepted answer

If you consider a closed system, this will be true, as dewpoint is related to the absolute moisture which is not a function of temperature. However, as username_3's answer demonstrates, the atmosphere is not a closed system. Even devoid of fronts and severe weather there are still pressure gradients which result in wind. Wind advects moisture and so if there is wind the moisture (dew point) can change.

Furthermore if we consider surface fluxes that statement becomes even less true. With no advection if we have vegetation or standing water on the surface we can increase the dew point just through evapotranspiration.


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### Answer by username_3 on 2015-08-12. Score: 2

From a review of weather observations, that statement is false.

Below are the synoptic weather maps for Australia for 11 August 2015 and [12 August 2015](http://www.bom.gov.au/australia/charts/synoptic_col.shtml). There are no weather fronts, or adverse weather in the western two-thirds of the continent.

[![Aus synopic map 20150811](https://i.sstatic.net/3BHgI.png)](https://i.sstatic.net/3BHgI.png)

[![enter image description here](https://i.sstatic.net/6Tjx3.png)](https://i.sstatic.net/6Tjx3.png)

Alice Springs (lat:-23.8, long: 133.89) is in the centre of the continent. It's [weather observations](http://www.bom.gov.au/products/IDD60801/IDD60801.94326.shtml) for 11 August 2015 reveal the temperature ranged between $5.8$ $^oC$ and $26.0$ $^oC$ and the dew point range was between $-18.8$ $^oC$ and $-2.5$ $^oC$.

Similarly for [Darwin](http://www.bom.gov.au/products/IDD60901/IDD60901.94120.shtml) (lat: -12.42, long: 130.89), which is located on the coast in the sub tropics, in the central north of the country, the temperature range for 11 August 2015 was $19.7$ $^oC$ to $30.1$ $^oC$, while the dew point range was $15.4$ $^oC$ to $19.8$ $^oC$.

[Perth](http://www.bom.gov.au/products/IDW60901/IDW60901.94610.shtml) (lat: -31.93, long: 115.98), on the southern western coast has a temperate Mediterranean climate. It's temperature range was $10.2$ $^oC$ to $17.6$ $^oC$ and the dew point range was $5.7$ $^oC$ to $11.7$ $^oC$.

[Adelaide](http://www.bom.gov.au/products/IDS60901/IDS60901.94672.shtml) (lat: -34.95, long: 138.52), on the southern coast, in the centre region , also has a temperate climate and its temperature ranged from $7.6$ $^oC$ to $15.4$ $^oC$ and the dew point range was $-0.3$ $^oC$ to $8.5$ $^oC$.

Lastly, [Brisbane](http://www.bom.gov.au/products/IDQ60901/IDQ60901.94578.shtml) (lat: -27.39, long: 153.13) which is on the east coast had temperatures between $8.2$ $^oC$ and $21.9$ $^oC$ and the dew point varied between $6.9$ $^oC$ and $15.8$ $^oC$.

All these weather observations show significant variance in the dew point for these locations given the respective temperature ranges and the lack of weather fronts and adverse weather systems.


---

