Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 56%
Humidity Trend -1% /hr
24hr Mean Humidity 72%
Wet-Bulb Temperature 15.7 °C
Absolute Humidity 10.25 gm-3
Air Density 1207.46 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 55%
12:33
51%
15:59
Maximum 95%
07:52
82%
04:01
Mean 82%
70%
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 (09-17)
Measure 7-day Month 31-day Year 365-day Overall Sep 24th Sep
Lowest
Min
51%
23rd
37%
2nd
37%
2nd
21%
25th Mar
21%
25th Mar
21%
25th Mar 2017
24%
Day 8, 2012
45%
2014
Highest
Max
97%
22nd
97%
4th
97%
22nd
97%
4th Sep
97%
22nd Sep
98%
6th Feb 2009
98%
Day 15, 2009
98%
2012
Highest
Min
70%
20th
80%
4th
80%
4th
84%
31st Jan
84%
31st Jan
98%
23rd Dec 2009
92%
Day 20, 2014
72%
2013
Lowest
Max
82%
23rd
80%
2nd
73%
27th
67%
25th Apr
67%
25th Apr
56%
20th Jul 2010
73%
Day 1, 2013
81%
2016
Lowest
Mean
70%
23rd
59%
2nd
58%
27th
48%
25th Apr
48%
25th Apr
39%
2nd May 2013
54%
Day 8, 2012
64%
2016
Highest
Mean
85%
19th
90%
4th
90%
4th
90%
4th Sep
90%
4th Sep
98%
23rd Dec 2009
96%
Day 13, 2013
90%
2013
Averages                
Mean 80% 78% 75% 69% 71% 75% 76% 78%
Mean
Minimum
60% 59% 56% 55% 58% 58% 57% 57%
Mean
Maximum
93% 92% 90% 82% 82% 88% 90% 93%

Past Year Monthly Averages and Extremes (September 2016 - August 2017)
Extremes Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
Lowest
Min
36%
13th
46%
6th
47%
28th
51%
4th
45%
20th
47%
23rd
21%
25th
29%
9th
35%
22nd
35%
19th
32%
7th
33%
13th
Highest
Max
95%
5th
88%
27th
83%
19th
90%
12th
88%
29th
88%
5th
88%
8th
86%
3rd
89%
17th
88%
28th
87%
12th
87%
31st
Highest
Min
83%
10th
79%
25th
79%
14th
81%
30th
84%
31st
81%
1st
73%
18th
67%
4th
78%
17th
78%
28th
73%
24th
79%
21st
Lowest
Max
80%
14th
69%
6th
72%
28th
78%
4th
76%
20th
70%
24th
71%
2nd
67%
25th
74%
8th
68%
26th
72%
3rd
70%
13th
Lowest
Mean
62%
13th
60%
6th
61%
28th
68%
26th
66%
21st
60%
24th
50%
25th
48%
25th
56%
22nd
52%
26th
51%
17th
51%
13th
Highest
Mean
93%
10th
81%
25th
80%
15th
83%
30th
85%
31st
84%
10th
81%
20th
76%
4th
86%
17th
84%
28th
79%
24th
84%
9th
Averages Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
Mean 75% 75% 75% 78% 77% 78% 70% 60% 69% 63% 65% 67%
Mean
Minimum
59% 64% 66% 73% 69% 68% 55% 46% 53% 47% 48% 51%
Mean
Maximum
87% 82% 80% 82% 83% 85% 82% 76% 83% 79% 80% 82%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 16/17 70%
83%
78%
Spring 2017 51%
80%
66%
Summer 2017 49%
81%
65%
Autumn 2016 63%
83%
75%

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
69%
2017
71%
Ending 17th Jul 2017
Most
Humid
96%
Ending 27th Nov 2014
92%
Dec 2009
79%
2013
93%
Ending 20th Jan 2010
77%
2010
79%
Ending 7th Apr 2010
Lowest
Mean
Daily-Min
32%
Ending 19th Jul 2013
42%
Jul 2013
49%
2012
40%
Ending 15th May 2011
55%
2017
56%
Ending 11th Jul 2015
Highest
Mean
Daily-Min
92%
Ending 27th Nov 2014
84%
Dec 2009
60%
2013
86%
Ending 20th Jan 2010
62%
2010
62%
Ending 8th Apr 2010
Lowest
Mean
Daily-Max
73%
Ending 25th Apr 2017
76%
Apr 2017
87%
2016
76%
Ending 30th Apr 2017
82%
2017
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 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 26%
19th Apr 2011
65%
27th May 2013
45%
17th Jul 2013
9 26%
2nd May 2013
65%
1st Jul 2015
45%
30th Jun 2015
10 27%
25th May 2011
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%
Nov 2011
95%
Jan 2010
89%
Nov 2011
6 77%
Dec 2012
95%
Oct 2012
88%
Dec 2010
7 77%
Nov 2010
95%
Nov 2011
88%
Jan 2014
8 76%
Jan 2013
95%
Oct 2013
87%
Dec 2012
9 76%
Jan 2011
95%
Nov 2009
87%
Nov 2010
10 76%
Jan 2014
95%
Nov 2009
87%
Jan 2013
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 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 84%
Day 9, 2013
98%
Day 27, 2010
93%
Day 10, 2016
4 83%
Day 15, 2009
98%
Day 30, 2010
92%
Day 14, 2013
5 83%
Day 29, 2014
98%
Day 28, 2011
92%
Day 9, 2013
Least Humid Days in September
Rank Min Max Mean
1 24%
Day 8, 2012
73%
Day 1, 2013
54%
Day 8, 2012
2 30%
Day 7, 2012
75%
Day 1, 2012
57%
Day 7, 2012
3 30%
Day 9, 2012
77%
Day 6, 2009
58%
Day 11, 2012
4 36%
Day 13, 2016
77%
Day 5, 2012
58%
Day 1, 2013
5 37%
Day 6, 2012
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.