# Relative humidity explained

### Yearly chart

The annual graph allows the different months' relative humidity ranges to be evaluated. Moreover, overlaying the average value trend for each day helps visualize the differences between the minimum and maximum daily values for the investigated location.

The humidity comfort band is overlaid, considering 30-70% RH the comfortable range. With these trends, climates can be assessed, whether too dry or too humid, then evaluating design solutions that include humidification or dehumidification system.

<figure><img src="/files/bssE6ppzQEUdFjfBPuRM" alt=""><figcaption><p>Yearly relative humidity trend in four common climatic conditions: hot dry, tropical, temperate, and continental</p></figcaption></figure>

Outdoor relative humidity varies greatly depending on the amount of rainfall. As expected, hot dry and tropical climates have diametrically opposite trends, always outside the comfort range, and some measures must be taken to recreate comfortable situations in buildings.

### Daily chart

Monthly [scatterplots](https://en.wikipedia.org/wiki/Scatter_plot) show all hourly relative humidity. The humidity excursion is much more evident than in the annual graphs. Daily medians, i.e., the most frequently occurring values, help evaluate the outliers.

<figure><img src="/files/CxzSkCbLL1owCY41Gd4H" alt=""><figcaption><p>Daily relative humidity trend in four common climatic conditions: hot dry, tropical, temperate, and continental</p></figcaption></figure>

Typical monthly days are useful to study relative humidity patterns. It is possible to read the variability of rainfall in a given location, from the constant high rates of tropical climate to the confusing and variable patterns of continental ones.

### Heatmap

Heatmap is another very useful method for evaluating relative humidity excursion over a year (by evaluating the horizontal gradient) or over individual days (by evaluating the vertical gradient).

<figure><img src="/files/bRoEKkH8tgSttRNJbFVc" alt=""><figcaption><p>Annual relative humidity heatmap for four common climatic conditions: hot dry, tropical, temperate, and continental</p></figcaption></figure>

The four heatmaps give a clear idea of the comparison of the four climate types. Albeit little differences in the percentage scale, observations can be made about relative humidity trends, especially between day and night. Except on rainy days, we can see how daily sunshine decreases relative humidity, even in tropical climates.

### Descriptive statistics

The last tool for relative humidity assessment is the statistics table. The earlier graphically made evaluations can be supported by the numbers. The following are listed, for each month:

* the relative humidity means;
* the [standard deviations](https://en.wikipedia.org/wiki/Standard_deviation);
* the minimum values;
* the [percentiles values](https://en.wikipedia.org/wiki/Percentile) (1%, 25%, 50%, 75%, 99%);
* the maximum values.
*

```
<figure><img src="../../../.gitbook/assets/Desc stat RH.png" alt=""><figcaption><p>Descriptive statistics of relative humidity trend in a temperate climate, Berkeley (USA)</p></figcaption></figure>
```


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