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Detailed Humidity Data
Current/Latest | |
| Measure | Value |
| Relative Humidity | 84% |
| Rel. Humidity Trend | -1% /hr |
| 24hr Average RH | 69% |
| Yesterday Average RH | 69% |
| Week Average RH | 73% |
| Month Average RH | 74% |
| --- | --- |
| Dew Point | 8.7 °C |
| Dew Point Trend | +0.0 °C /hr |
| 24hr Avg Dew Point | 7.7 °C |
| Yesterday Avg Dew Point | 8.6 °C |
| Week Avg Dew Point | 12.9 °C |
| Month Avg Dew Point | 11.5 °C |
| --- | --- |
| Wet-Bulb Temperature | 10.0 °C |
| Absolute Humidity | 6.1 kgm-3 |
| Air Density | 1.24 kgm-3 |
Current Day/Month/Year Records | ||
| Measure | Value | Time/Date |
| Min RH Today | 77% | 00:00 |
| Max RH Today | 85% | 05:13 |
| Min RH Yesterday | 53% | 18:16 |
| Max RH Yesterday | 88% | 02:02 |
| Min RH This Month | 34% | Day 2 |
| Max RH This Month | 97% | Day 3 |
| Min RH This Year | 24% | 23rd June |
| Max RH This Year | 98% | Occurs regularly |
| --- | --- | --- |
| Min Dew Point Today | 7.6 °C | 01:37 |
| Max Dew Point Today | 8.7 °C | 06:41 |
| Min Dew Point Yesterday | 5.8 °C | 12:00 |
| Max Dew Point Yesterday | 16.1 °C | 02:02 |
| Min Dew Point This Month | 5.2 °C | Day 13 |
| Max Dew Point This Month | 17.7 °C | Day 11 |
| Min Dew Point This Year | -9.3 °C | 28th Feb |
| Max Dew Point This Year | 20.9 °C | 27th July |
All-time Records | ||
| Measure | Value | Time/Date |
| Lowest Relative Humidity | 24% | 23rd June 2018 |
| Highest Relative Humidity | 98% | Occurs regularly |
| Lowest RH Daily Mean | 39% | 2nd May 2013 |
| Highest RH Daily Mean | 98% | Several instances |
| Lowest RH Monthly Mean | 60% | May 2011 |
| Highest RH Monthly Mean | 92% | Dec 2009 |
| --- | --- | --- |
| Lowest Dew Point | -9.3 °C | 28th Feb 2018 |
| Highest Dew Point | 20.9 °C | 27th July 2018 |
| Lowest Dew Point Daily Mean | -9.7 °C | 2nd Feb 2012 |
| Highest Dew Point Daily Mean | 19.2 °C | 12th May 2016 |
| Lowest Dew Point Monthly Mean | -0.5 °C | Dec 2010 |
| Highest Dew Point Monthly Mean | 13.5 °C | July 2018 |
Note 1: Valid humidity records began in February 2009
Note 2: 98% is the physical limit of the hygrometer (measuring RH); in reality this tends to means 100% saturation of the air
NB: Daily dew point max/mins for the current year (and all other years on record) can be viewed
here.
Relative humidity max/mins are here
A note on the different measures of humidity:
The Dew Point (or frost point if the temperature is < 0.0 °Cis the saturation temperature of a parcel of air, i.e. the point at which water condenses out.
It is the temperature at which an object would need to be
for dew to form on it (dew forms because certain objects - like cars - cool more rapidly than the air, enabling them to
reach the dew point). It is directly proportional to the specific humidity, and very well correlated to the absolute humidity.
In everyday terms, high dew points are more uncomfortable as sweating is less effective.
Relative Humidity, on the other hand, is rather more abstract and has a very technical definition:
the ratio of the partial pressure of water vapour in the air to the saturated vapour pressure of that water.
The saturated vapour pressure is proportional to the air temperature, and the partial pressure indicates how much water vapour the air contains,
so at a given temperature, the RH is entirely dependent on this partial pressure, making the RH useful in determining the extent to which the air is water-saturated.
For example: When it rains the relative humidity will increase, but the dew point may not, as the temperature will usually fall as well.
If the dew point is the same when the RH increases, the air has the same amount of water but it is cooler,
so it is more saturated, as less water vapour can exist in cooler air.
Simply (and concisely!): Dew point is a rough measure of how much water vapour is physically in the air;
relative humidity is just a measure of the degree to which the air is full of water vapour (i.e. its saturation).
One is an absolute measure, the other is relative.