Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 80%
Humidity Trend -7% /hr
24hr Mean Humidity 83%
Wet-Bulb Temperature 17.6 °C
Absolute Humidity 13.81 gm-3
Air Density 1212.88 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 80%
10:48
73%
13:41
Maximum 93%
08:37
91%
06:58
Mean 90%
82%
Last 6hrs  LondonHumidity31-day chart of mean LondonHumidity 31-day chart of min LondonHumidity 31-day chart of max LondonHumidity
Averages, Extremes and Records
Current Station Lifetime (09-18)
Measure 7-day Month 31-day Year 365-day Overall May 26th May
Lowest
Min
40%
21st
28%
7th
28%
7th
25%
19th Apr
25%
19th Apr
21%
25th Mar 2017
26%
Day 2, 2013
29%
2012
Highest
Max
94%
24th
95%
19th
95%
19th
98%
4th Jan
98%
21st Jan
98%
6th Feb 2009
98%
Day 2, 2014
94%
2009
Highest
Min
80%
Today
80%
Today
88%
28th
93%
11th Jan
94%
20th Dec
98%
23rd Dec 2009
91%
Day 28, 2014
80%
Today
Lowest
Max
84%
22nd
73%
15th
73%
15th
72%
17th Apr
68%
26th Jun
56%
20th Jul 2010
56%
Day 2, 2013
75%
2010
Lowest
Mean
70%
22nd
54%
7th
54%
7th
54%
19th Apr
51%
13th Aug
39%
2nd May 2013
39%
Day 2, 2013
50%
2013
Highest
Mean
90%
Today
90%
Today
91%
28th
95%
9th Apr
96%
20th Dec
98%
23rd Dec 2009
96%
Day 28, 2014
90%
Today
Averages                
Mean 78% 68% 70% 79% 77% 75% 67% 66%
Mean
Minimum
59% 47% 50% 64% 62% 59% 48% 46%
Mean
Maximum
91% 89% 89% 91% 89% 88% 85% 85%

Past Year Monthly Averages and Extremes (May 2017 - April 2018)
Extremes May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Lowest
Min
35%
22nd
35%
19th
32%
7th
33%
13th
37%
2nd
51%
5th
52%
1st
69%
8th
59%
16th
47%
25th
42%
26th
25%
19th
Highest
Max
89%
17th
88%
28th
87%
12th
87%
31st
97%
4th
98%
15th
98%
3rd
98%
20th
98%
4th
96%
14th
96%
3rd
97%
11th
Highest
Min
78%
17th
78%
28th
73%
24th
79%
21st
80%
4th
92%
26th
89%
15th
94%
20th
93%
11th
88%
19th
90%
3rd
93%
9th
Lowest
Max
74%
8th
68%
26th
72%
3rd
70%
13th
80%
2nd
82%
4th
82%
13th
83%
6th
83%
14th
80%
25th
80%
19th
72%
17th
Lowest
Mean
56%
22nd
52%
26th
51%
17th
51%
13th
59%
2nd
71%
5th
72%
23rd
75%
6th
73%
17th
65%
25th
61%
26th
54%
19th
Highest
Mean
86%
17th
84%
28th
79%
24th
84%
9th
90%
4th
96%
26th
93%
15th
96%
20th
95%
21st
93%
19th
94%
3rd
95%
9th
Averages May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Mean 69% 63% 65% 67% 79% 82% 84% 88% 85% 80% 81% 78%
Mean
Minimum
53% 47% 48% 51% 60% 69% 71% 79% 75% 65% 67% 62%
Mean
Maximum
83% 79% 80% 82% 92% 92% 93% 94% 93% 91% 92% 89%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 17/18 73%
93%
84%
Spring 2017 60%
88%
76%
Summer 2017 49%
81%
65%
Autumn 2017 67%
93%
82%

View daily tables of min / max / mean Humidity data for the past year
View monthly tables of min / max / mean Humidity data for all months in the station history.

Last 24hrs  LondonHumidity 12month mean  LondonHumidity 12month min  LondonHumidity 12month max  LondonHumidity
Record Period Averages
Measure 7-day Month May 31-day Year 365-day
Least
Humid
50%
Ending 9th May 2016
60%
May 2011
60%
2011
58%
Ending 6th May 2011
73%
2016
71%
Ending 17th Jul 2017
Most
Humid
96%
Ending 27th Nov 2014
92%
Dec 2009
72%
2012
93%
Ending 20th Jan 2010
79%
2018
79%
Ending 7th Apr 2010
Lowest
Mean
Daily-Min
32%
Ending 19th Jul 2013
42%
Jul 2013
42%
2011
40%
Ending 15th May 2011
57%
2015
56%
Ending 11th Jul 2015
Highest
Mean
Daily-Min
92%
Ending 27th Nov 2014
84%
Dec 2009
54%
2012
86%
Ending 20th Jan 2010
64%
2018
62%
Ending 8th Apr 2010
Lowest
Mean
Daily-Max
73%
Ending 25th Apr 2017
76%
Apr 2017
80%
2011
76%
Ending 30th Apr 2017
85%
2016
82%
Ending 2nd Sep 2017
Highest
Mean
Daily-Max
98%
Ending 17th Jan 2010
97%
Dec 2009
89%
Current
97%
Ending 28th Dec 2009
91%
2018
92%
Ending 1st Mar 2010

Ranked Historical Humidity Data

Most Humid Days
Rank Min Max Mean
1 98%
23rd Dec 2009
98%
6th Feb 2009
98%
23rd Dec 2009
2 98%
24th Dec 2009
98%
9th Feb 2009
98%
24th Dec 2009
3 98%
30th Dec 2009
98%
10th Feb 2009
98%
30th Dec 2009
4 98%
14th Jan 2010
98%
13th Feb 2009
98%
14th Jan 2010
5 98%
15th Jan 2010
98%
7th Aug 2009
98%
15th Jan 2010
6 98%
29th Dec 2010
98%
8th Aug 2009
98%
29th Dec 2010
7 98%
22nd Oct 2012
98%
15th Sep 2009
98%
30th Dec 2010
8 98%
23rd Oct 2012
98%
16th Sep 2009
98%
20th Nov 2011
9 98%
11th Feb 2013
98%
7th Oct 2009
98%
21st Nov 2011
10 98%
8th Mar 2013
98%
10th Oct 2009
98%
22nd Oct 2012
Least Humid Days
Rank Min Max Mean
1 21%
25th Mar 2017
56%
20th Jul 2010
39%
2nd May 2013
2 22%
15th Jul 2013
56%
2nd May 2013
41%
5th May 2016
3 22%
18th Jul 2016
61%
28th Mar 2012
41%
15th Jul 2013
4 24%
8th Sep 2012
62%
6th Jan 2009
43%
20th Jul 2010
5 24%
30th Jun 2015
63%
21st Feb 2013
43%
28th Mar 2012
6 24%
10th Jul 2015
64%
31st Jan 2009
44%
10th Jul 2015
7 24%
19th Jul 2015
65%
2nd Feb 2012
44%
1st Jul 2015
8 25%
19th Apr 2018
65%
27th May 2013
45%
17th Jul 2013
9 26%
19th Apr 2011
65%
1st Jul 2015
45%
30th Jun 2015
10 26%
2nd May 2013
65%
11th Jul 2015
45%
8th May 2016


Most Humid Months
Rank Min Max Mean
1 84%
Dec 2009
97%
Dec 2009
92%
Dec 2009
2 82%
Jan 2010
96%
Nov 2014
90%
Nov 2014
3 81%
Nov 2014
96%
Feb 2010
90%
Jan 2010
4 80%
Dec 2010
96%
Jan 2014
89%
Feb 2010
5 79%
Dec 2017
95%
Jan 2010
89%
Nov 2011
6 79%
Nov 2011
95%
Oct 2012
88%
Dec 2010
7 77%
Dec 2012
95%
Nov 2011
88%
Jan 2014
8 77%
Nov 2010
95%
Oct 2013
88%
Dec 2017
9 76%
Jan 2013
95%
Nov 2009
87%
Dec 2012
10 76%
Jan 2011
95%
Nov 2009
87%
Nov 2010
Least Humid Months
Rank Min Max Mean
1 42%
Jul 2013
76%
Apr 2017
60%
May 2011
2 42%
May 2011
79%
Jun 2017
60%
Apr 2017
3 42%
Jun 2015
80%
May 2011
61%
Jun 2015
4 43%
Jul 2014
80%
Apr 2011
61%
Jul 2013
5 43%
Jul 2015
80%
Apr 2011
62%
Apr 2011
6 44%
Jun 2014
80%
Jun 2015
63%
Jul 2015
7 44%
Apr 2015
80%
Jul 2017
63%
Jul 2010
8 44%
May 2015
81%
Jul 2010
63%
Jun 2017
9 44%
Apr 2011
82%
Jul 2015
64%
May 2015
10 44%
Aug 2013
82%
Dec 2016
64%
Apr 2015


Most Humid Days in May
Rank Min Max Mean
1 91%
Day 28, 2014
98%
Day 2, 2014
96%
Day 28, 2014
2 90%
Day 3, 2012
98%
Day 28, 2014
94%
Day 27, 2014
3 89%
Day 27, 2014
97%
Day 1, 2012
92%
Day 3, 2012
4 83%
Day 10, 2012
97%
Day 10, 2012
92%
Day 10, 2012
5 80%
Day 4, 2012
97%
Day 25, 2013
90%
Day 9, 2012
Least Humid Days in May
Rank Min Max Mean
1 26%
Day 2, 2013
56%
Day 2, 2013
39%
Day 2, 2013
2 27%
Day 25, 2011
65%
Day 27, 2013
41%
Day 5, 2016
3 27%
Day 8, 2016
66%
Day 1, 2011
45%
Day 8, 2016
4 28%
Day 5, 2016
67%
Day 20, 2011
46%
Day 25, 2011
5 28%
Day 7, 2018
67%
Day 5, 2016
47%
Day 27, 2013

Notes:

  • Valid humidity records began in February 2009
  • All figures, unless specified, relate to the period midnight-midnight, this being when daily extremes are reset
  • 98% is the physical limit of the hygrometer (measuring RH); in reality this tends to means 100% saturation of the air. This value is achieved fairly frequently, any record with this value is just the first instance it occurred in the relevant timeframe.

The different measures of humidity:
The Dew Point (or frost point if the temperature is < 0.0 °C  is 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.