Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 91%
Humidity Trend +2% /hr
24hr Mean Humidity 93%
Wet-Bulb Temperature 4.6 °C
Absolute Humidity 6.32 gm-3
Air Density 1297.47 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 88%
16:02
77%
14:39
Maximum 97%
10:51
94%
22:59
Mean 93%
88%
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 (09-22)
Measure 7-day Month 31-day Year 365-day Overall Jan 18th Jan
Lowest
Min
75%
13th
74%
6th
72%
21st
74%
6th Jan
20%
9th Jun
20%
9th Jun 2021
42%
Day 6, 2009
50%
2009
Highest
Max
97%
Today
97%
13th
98%
26th
97%
13th Jan
98%
26th Dec
98%
6th Feb 2009
98%
Day 6, 2010
98%
2010
Highest
Min
88%
Today
89%
11th
94%
26th
89%
11th Jan
94%
26th Dec
98%
23rd Dec 2009
98%
Day 14, 2010
95%
2010
Lowest
Max
94%
17th
91%
3rd
90%
21st
91%
3rd Jan
75%
8th Apr
56%
20th Jul 2010
62%
Day 6, 2009
82%
2017
Lowest
Mean
88%
17th
83%
5th
82%
21st
83%
5th Jan
57%
5th Apr
39%
2nd May 2013
52%
Day 6, 2009
70%
2017
Highest
Mean
93%
Today
93%
Today
96%
26th
93%
Today
96%
26th Dec
98%
23rd Dec 2009
98%
Day 14, 2010
98%
2010
Averages                
Mean 90% 88% 89% 88% 80% 76% 84% 84%
Mean
Minimum
82% 80% 82% 80% 66% 60% 74% 73%
Mean
Maximum
96% 94% 94% 94% 91% 89% 92% 93%

Past Year Monthly Averages and Extremes (January 2021 - December 2021)
Extremes Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Lowest
Min
69%
22nd
51%
13th
28%
30th
23%
23rd
40%
2nd
20%
9th
37%
20th
53%
24th
39%
7th
60%
1st
65%
7th
69%
8th
Highest
Max
97%
13th
98%
2nd
97%
3rd
94%
16th
95%
18th
97%
28th
96%
26th
95%
3rd
98%
26th
98%
18th
97%
3rd
98%
26th
Highest
Min
92%
27th
87%
1st
93%
3rd
65%
1st
73%
13th
92%
18th
79%
25th
76%
17th
86%
14th
85%
16th
87%
10th
94%
26th
Lowest
Max
88%
21st
75%
13th
83%
9th
75%
8th
79%
7th
77%
15th
85%
17th
87%
16th
86%
3rd
88%
23rd
87%
21st
83%
8th
Lowest
Mean
80%
21st
64%
13th
60%
30th
57%
5th
58%
7th
57%
2nd
67%
18th
72%
11th
70%
7th
76%
24th
76%
7th
76%
8th
Highest
Mean
95%
13th
92%
4th
95%
3rd
77%
1st
87%
17th
94%
18th
90%
25th
86%
22nd
93%
14th
92%
18th
92%
10th
96%
19th
Averages Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean 90% 82% 78% 67% 75% 75% 78% 80% 82% 85% 85% 88%
Mean
Minimum
82% 72% 64% 46% 54% 58% 61% 64% 66% 72% 76% 81%
Mean
Maximum
94% 90% 89% 86% 90% 90% 91% 91% 93% 93% 92% 93%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 20/21 79%
92%
86%
Spring 2021 54%
88%
74%
Summer 2021 61%
91%
78%
Autumn 2021 72%
93%
84%

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 Jan 31-day Year 365-day
Least
Humid
50%
Ending 9th May 2016
60%
May 2011
73%
2009
58%
Ending 6th May 2011
73%
2016
71%
Ending 17th Jul 2017
Most
Humid
96%
Ending 27th Nov 2014
92%
Dec 2009
90%
2010
93%
Ending 20th Jan 2010
88%
2022
81%
Ending 28th Sep 2021
Lowest
Mean
Daily-Min
32%
Ending 19th Jul 2013
40%
May 2020
59%
2009
37%
Ending 21st Jul 2018
57%
2015
56%
Ending 11th Jul 2015
Highest
Mean
Daily-Min
92%
Ending 27th Nov 2014
84%
Dec 2009
82%
2021
86%
Ending 20th Jan 2010
80%
2022
67%
Ending 28th Sep 2021
Lowest
Mean
Daily-Max
73%
Ending 25th Apr 2017
76%
Apr 2017
83%
2017
76%
Ending 30th Apr 2017
85%
2016
82%
Ending 2nd Sep 2017
Highest
Mean
Daily-Max
98%
Ending 17th Jan 2010
97%
Dec 2009
96%
2014
97%
Ending 28th Dec 2009
94%
2022
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%
Dec 2021
95%
Jan 2010
89%
Dec 2020
6 81%
Nov 2014
95%
Oct 2012
89%
Nov 2019
7 80%
Current
95%
Nov 2011
89%
Feb 2010
8 80%
Dec 2010
95%
Nov 2019
89%
Nov 2011
9 80%
Nov 2019
95%
Oct 2013
88%
Current
10 79%
Dec 2019
95%
Nov 2009
88%
Dec 2010
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 January
Rank Min Max Mean
1 98%
Day 14, 2010
98%
Day 6, 2010
98%
Day 14, 2010
2 98%
Day 15, 2010
98%
Day 11, 2010
98%
Day 15, 2010
3 96%
Day 30, 2014
98%
Day 12, 2010
98%
Day 30, 2014
4 96%
Day 4, 2015
98%
Day 13, 2010
98%
Day 18, 2010
5 95%
Day 18, 2010
98%
Day 14, 2010
98%
Day 19, 2010
Least Humid Days in January
Rank Min Max Mean
1 42%
Day 6, 2009
62%
Day 6, 2009
52%
Day 6, 2009
2 42%
Day 11, 2009
64%
Day 31, 2009
56%
Day 31, 2009
3 45%
Day 20, 2017
68%
Day 3, 2009
58%
Day 3, 2009
4 46%
Day 5, 2009
72%
Day 4, 2009
62%
Day 4, 2009
5 47%
Day 3, 2009
76%
Day 28, 2011
63%
Day 22, 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.