Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 71%
Humidity Trend +2% /hr
24hr Mean Humidity 64%
Wet-Bulb Temperature 6.6 °C
Absolute Humidity 6.21 gm-3
Air Density 1276.70 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 43%
12:23
38%
16:29
Maximum 82%
07:16
87%
00:01
Mean 64%
67%
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 April 13th Apr
Lowest
Min
38%
12th
27%
5th
27%
5th
27%
5th Apr
26%
7th Aug
21%
25th Mar 2017
25%
Day 19, 2018
39%
2016
Highest
Max
88%
11th
89%
1st
94%
23rd
98%
2nd Feb
98%
4th Feb
98%
6th Feb 2009
98%
Day 29, 2012
97%
2009
Highest
Min
62%
10th
65%
1st
78%
28th
93%
3rd Mar
94%
7th Dec
98%
23rd Dec 2009
94%
Day 17, 2009
78%
2018
Lowest
Max
75%
8th
75%
8th
75%
8th
75%
13th Feb
71%
22nd Jul
56%
20th Jul 2010
66%
Day 21, 2011
71%
2017
Lowest
Mean
64%
Today
57%
5th
57%
5th
57%
5th Apr
54%
30th Jul
39%
2nd May 2013
48%
Day 21, 2011
54%
2016
Highest
Mean
74%
10th
77%
1st
86%
18th
95%
3rd Mar
95%
7th Dec
98%
23rd Dec 2009
96%
Day 11, 2009
87%
2013
Averages                
Mean 68% 68% 73% 81% 78% 76% 68% 69%
Mean
Minimum
48% 49% 56% 70% 63% 60% 49% 50%
Mean
Maximum
83% 84% 87% 90% 90% 89% 85% 86%

Past Year Monthly Averages and Extremes (April 2020 - March 2021)
Extremes Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar
Lowest
Min
25%
5th
28%
21st
33%
2nd
29%
31st
26%
7th
44%
14th
55%
1st
61%
2nd
75%
5th
69%
22nd
51%
13th
28%
30th
Highest
Max
96%
26th
93%
7th
94%
13th
95%
8th
98%
17th
96%
1st
96%
2nd
97%
5th
97%
7th
97%
13th
98%
2nd
97%
3rd
Highest
Min
72%
28th
61%
10th
71%
10th
80%
9th
90%
15th
81%
3rd
92%
4th
90%
29th
94%
7th
92%
27th
87%
1st
93%
3rd
Lowest
Max
73%
14th
72%
11th
80%
24th
71%
22nd
79%
3rd
81%
27th
89%
28th
90%
3rd
86%
25th
88%
21st
75%
13th
83%
9th
Lowest
Mean
53%
5th
55%
22nd
57%
2nd
54%
30th
56%
7th
68%
10th
77%
19th
78%
2nd
82%
25th
80%
21st
64%
13th
60%
30th
Highest
Mean
90%
28th
80%
1st
85%
18th
90%
8th
93%
15th
87%
30th
93%
4th
93%
27th
95%
7th
95%
13th
92%
4th
95%
3rd
Averages Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar
Mean 67% 62% 71% 71% 74% 76% 87% 87% 89% 90% 82% 78%
Mean
Minimum
46% 40% 52% 53% 56% 57% 75% 77% 84% 82% 72% 64%
Mean
Maximum
86% 84% 88% 87% 89% 90% 93% 94% 93% 94% 90% 89%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 20/21 79%
93%
87%
Spring 2020 50%
87%
69%
Summer 2020 53%
88%
72%
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 April 31-day Year 365-day
Least
Humid
50%
Ending 9th May 2016
60%
May 2011
60%
2017
58%
Ending 6th May 2011
73%
2016
71%
Ending 17th Jul 2017
Most
Humid
96%
Ending 27th Nov 2014
92%
Dec 2009
78%
2018
93%
Ending 20th Jan 2010
81%
2021
79%
Ending 7th Apr 2010
Lowest
Mean
Daily-Min
32%
Ending 19th Jul 2013
40%
May 2020
44%
2015
37%
Ending 21st Jul 2018
57%
2015
56%
Ending 11th Jul 2015
Highest
Mean
Daily-Min
92%
Ending 27th Nov 2014
84%
Dec 2009
62%
2018
86%
Ending 20th Jan 2010
70%
2021
63%
Ending 12th Apr 2021
Lowest
Mean
Daily-Max
73%
Ending 25th Apr 2017
76%
Apr 2017
76%
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
90%
2009
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 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
63%
2nd Jul 2018
43%
2nd Jul 2018
7 24%
19th Jul 2015
64%
31st Jan 2009
44%
10th Jul 2015
8 24%
23rd Jun 2018
65%
2nd Feb 2012
44%
1st Jul 2015
9 25%
19th Apr 2018
65%
27th May 2013
45%
17th Jul 2013
10 25%
25th 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 April
Rank Min Max Mean
1 94%
Day 17, 2009
98%
Day 29, 2012
96%
Day 11, 2009
2 93%
Day 11, 2009
98%
Day 11, 2013
96%
Day 17, 2009
3 93%
Day 9, 2018
98%
Day 14, 2013
95%
Day 9, 2018
4 92%
Day 12, 2009
98%
Day 21, 2014
95%
Day 12, 2009
5 91%
Day 12, 2018
97%
Day 11, 2009
95%
Day 12, 2018
Least Humid Days in April
Rank Min Max Mean
1 25%
Day 19, 2018
66%
Day 21, 2011
48%
Day 21, 2011
2 25%
Day 5, 2020
66%
Day 17, 2014
48%
Day 15, 2015
3 26%
Day 19, 2011
67%
Day 25, 2017
48%
Day 25, 2017
4 27%
Day 15, 2015
68%
Day 23, 2017
50%
Day 22, 2011
5 27%
Day 5, 2021
69%
Day 11, 2017
51%
Day 19, 2017

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.