Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 86%
Humidity Trend +2% /hr
24hr Mean Humidity 77%
Wet-Bulb Temperature 9.5 °C
Absolute Humidity 8.49 gm-3
Air Density 1251.58 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 81%
00:03
56%
17:06
Maximum 86%
04:34
93%
08:45
Mean 83%
78%
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 (09-21)
Measure 7-day Month 31-day Year 365-day Overall Sep 28th Sep
Lowest
Min
56%
27th
39%
7th
39%
7th
20%
9th Jun
20%
9th Jun
20%
9th Jun 2021
24%
Day 8, 2012
47%
2018
Highest
Max
98%
26th
98%
26th
98%
26th
98%
2nd Feb
98%
26th Sep
98%
6th Feb 2009
98%
Day 15, 2009
98%
2011
Highest
Min
86%
25th
86%
14th
86%
25th
93%
3rd Mar
94%
7th Dec
98%
23rd Dec 2009
92%
Day 20, 2014
81%
Today
Lowest
Max
86%
Today
86%
3rd
86%
Today
75%
13th Feb
75%
8th Apr
56%
20th Jul 2010
73%
Day 1, 2013
84%
2016
Lowest
Mean
78%
27th
70%
7th
70%
7th
57%
5th Apr
57%
5th Apr
39%
2nd May 2013
54%
Day 8, 2012
68%
2018
Highest
Mean
90%
25th
93%
14th
93%
14th
95%
3rd Mar
95%
7th Dec
98%
23rd Dec 2009
96%
Day 13, 2013
90%
2010
Averages                
Mean 83% 82% 82% 79% 81% 76% 76% 79%
Mean
Minimum
71% 67% 67% 63% 67% 60% 58% 61%
Mean
Maximum
93% 92% 92% 90% 91% 89% 91% 92%

Past Year Monthly Averages and Extremes (September 2020 - August 2021)
Extremes Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
Lowest
Min
44%
14th
55%
1st
61%
2nd
75%
5th
69%
22nd
51%
13th
28%
30th
23%
23rd
40%
2nd
20%
9th
37%
20th
53%
24th
Highest
Max
96%
1st
96%
2nd
97%
5th
97%
7th
97%
13th
98%
2nd
97%
3rd
94%
16th
95%
18th
97%
28th
96%
26th
95%
3rd
Highest
Min
81%
3rd
92%
4th
90%
29th
94%
7th
92%
27th
87%
1st
93%
3rd
65%
1st
73%
13th
92%
18th
79%
25th
76%
17th
Lowest
Max
81%
27th
89%
28th
90%
3rd
86%
25th
88%
21st
75%
13th
83%
9th
75%
8th
79%
7th
77%
15th
85%
17th
87%
16th
Lowest
Mean
68%
10th
77%
19th
78%
2nd
82%
25th
80%
21st
64%
13th
60%
30th
57%
5th
58%
7th
57%
2nd
67%
18th
72%
11th
Highest
Mean
87%
30th
93%
4th
93%
27th
95%
7th
95%
13th
92%
4th
95%
3rd
77%
1st
87%
17th
94%
18th
90%
25th
86%
22nd
Averages Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
Mean 76% 87% 87% 89% 90% 82% 78% 67% 75% 75% 78% 80%
Mean
Minimum
57% 75% 77% 84% 82% 72% 64% 46% 54% 58% 61% 64%
Mean
Maximum
90% 93% 94% 93% 94% 90% 89% 86% 90% 90% 91% 91%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 20/21 79%
93%
87%
Spring 2021 54%
88%
74%
Summer 2021 61%
91%
78%
Autumn 2020 70%
93%
83%

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 Sep 31-day Year 365-day
Least
Humid
50%
Ending 9th May 2016
60%
May 2011
69%
2012
58%
Ending 6th May 2011
73%
2016
71%
Ending 17th Jul 2017
Most
Humid
96%
Ending 27th Nov 2014
92%
Dec 2009
82%
Current
93%
Ending 20th Jan 2010
79%
2021
81%
Ending Today
Lowest
Mean
Daily-Min
32%
Ending 19th Jul 2013
40%
May 2020
49%
2012
37%
Ending 21st Jul 2018
57%
2015
56%
Ending 11th Jul 2015
Highest
Mean
Daily-Min
92%
Ending 27th Nov 2014
84%
Dec 2009
67%
Current
86%
Ending 20th Jan 2010
63%
2021
67%
Ending Today
Lowest
Mean
Daily-Max
73%
Ending 25th Apr 2017
76%
Apr 2017
87%
2016
76%
Ending 30th Apr 2017
85%
2016
82%
Ending 2nd Sep 2017
Highest
Mean
Daily-Max
98%
Ending 17th Jan 2010
97%
Dec 2009
94%
2014
97%
Ending 28th Dec 2009
91%
2009
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 20%
9th Jun 2021
56%
20th Jul 2010
39%
2nd May 2013
2 21%
25th Mar 2017
56%
2nd May 2013
41%
5th May 2016
3 22%
15th Jul 2013
61%
28th Mar 2012
41%
15th Jul 2013
4 22%
18th Jul 2016
62%
6th Jan 2009
43%
20th Jul 2010
5 23%
23rd Apr 2021
63%
21st Feb 2013
43%
28th Mar 2012
6 24%
8th Sep 2012
63%
2nd Jul 2018
43%
2nd Jul 2018
7 24%
30th Jun 2015
64%
31st Jan 2009
44%
10th Jul 2015
8 24%
10th Jul 2015
65%
2nd Feb 2012
44%
1st Jul 2015
9 24%
19th Jul 2015
65%
27th May 2013
45%
17th Jul 2013
10 24%
23rd Jun 2018
65%
1st Jul 2015
45%
30th Jun 2015


Most Humid Months
Rank Min Max Mean
1 84%
Dec 2009
97%
Dec 2009
92%
Dec 2009
2 84%
Dec 2020
96%
Nov 2014
90%
Nov 2014
3 82%
Jan 2021
96%
Feb 2010
90%
Jan 2010
4 82%
Jan 2010
96%
Jan 2014
90%
Jan 2021
5 81%
Nov 2014
95%
Jan 2010
89%
Dec 2020
6 80%
Dec 2010
95%
Oct 2012
89%
Nov 2019
7 80%
Nov 2019
95%
Nov 2011
89%
Feb 2010
8 79%
Dec 2019
95%
Nov 2019
89%
Nov 2011
9 79%
Dec 2017
95%
Oct 2013
88%
Dec 2010
10 79%
Dec 2018
95%
Nov 2009
88%
Jan 2014
Least Humid Months
Rank Min Max Mean
1 40%
May 2020
76%
Apr 2017
60%
May 2011
2 41%
Jul 2018
79%
Jun 2017
60%
Apr 2017
3 42%
Jul 2013
80%
May 2011
61%
Jun 2015
4 42%
May 2011
80%
Apr 2011
61%
Jul 2013
5 42%
Jun 2015
80%
Apr 2011
62%
Apr 2011
6 43%
Jul 2014
80%
Jun 2015
62%
May 2020
7 43%
Jul 2015
80%
Jul 2017
62%
Jul 2018
8 44%
Jun 2014
81%
Jul 2010
63%
Jul 2015
9 44%
Apr 2015
82%
Jul 2015
63%
Jul 2010
10 44%
May 2015
82%
Dec 2016
63%
Jun 2017


Most Humid Days in September
Rank Min Max Mean
1 92%
Day 20, 2014
98%
Day 15, 2009
96%
Day 13, 2013
2 91%
Day 13, 2013
98%
Day 16, 2009
94%
Day 20, 2014
3 86%
Day 14, 2021
98%
Day 27, 2010
93%
Day 10, 2016
4 86%
Day 25, 2021
98%
Day 30, 2010
93%
Day 14, 2021
5 84%
Day 9, 2013
98%
Day 28, 2011
92%
Day 14, 2013
Least Humid Days in September
Rank Min Max Mean
1 24%
Day 8, 2012
73%
Day 1, 2013
54%
Day 8, 2012
2 29%
Day 27, 2018
75%
Day 1, 2012
57%
Day 7, 2012
3 30%
Day 7, 2012
77%
Day 6, 2009
58%
Day 11, 2012
4 30%
Day 9, 2012
77%
Day 5, 2012
58%
Day 1, 2013
5 33%
Day 26, 2018
78%
Day 13, 2011
58%
Day 19, 2012

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.