Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 78%
Humidity Trend +8% /hr
24hr Mean Humidity 82%
Wet-Bulb Temperature 9.4 °C
Absolute Humidity 7.99 gm-3
Air Density 1258.50 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 63%
14:45
64%
15:30
Maximum 96%
08:11
95%
07:36
Mean 82%
84%
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 Oct 19th Oct
Lowest
Min
61%
13th
46%
1st
29%
27th
24%
23rd Jun
24%
23rd Jun
21%
25th Mar 2017
35%
Day 3, 2011
45%
2011
Highest
Max
98%
16th
98%
16th
98%
16th
98%
4th Jan
98%
16th Oct
98%
6th Feb 2009
98%
Day 7, 2009
98%
2012
Highest
Min
95%
15th
95%
15th
95%
15th
95%
15th Oct
95%
15th Oct
98%
23rd Dec 2009
98%
Day 22, 2012
86%
2017
Lowest
Max
79%
13th
79%
13th
79%
13th
63%
2nd Jul
63%
2nd Jul
56%
20th Jul 2010
69%
Day 6, 2016
78%
2016
Lowest
Mean
69%
13th
66%
1st
62%
27th
43%
2nd Jul
43%
2nd Jul
39%
2nd May 2013
59%
Day 3, 2011
70%
2011
Highest
Mean
96%
15th
96%
15th
96%
15th
96%
15th Oct
96%
15th Oct
98%
23rd Dec 2009
98%
Day 22, 2012
94%
2012
Averages                
Mean 86% 82% 78% 75% 77% 75% 81% 83%
Mean
Minimum
74% 68% 61% 57% 61% 59% 67% 68%
Mean
Maximum
94% 92% 91% 90% 90% 88% 91% 92%

Past Year Monthly Averages and Extremes (October 2017 - September 2018)
Extremes Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Lowest
Min
51%
5th
52%
1st
69%
8th
59%
16th
47%
25th
42%
26th
25%
19th
28%
7th
24%
23rd
27%
2nd
28%
6th
29%
27th
Highest
Max
98%
15th
98%
3rd
98%
20th
98%
4th
96%
14th
96%
3rd
97%
11th
97%
31st
94%
4th
95%
14th
96%
26th
97%
3rd
Highest
Min
92%
26th
89%
15th
94%
20th
93%
11th
88%
19th
90%
3rd
93%
9th
85%
29th
74%
4th
69%
29th
70%
22nd
77%
22nd
Lowest
Max
82%
4th
82%
13th
83%
6th
83%
14th
80%
25th
80%
19th
72%
17th
73%
15th
70%
24th
63%
2nd
78%
8th
83%
14th
Lowest
Mean
71%
5th
72%
23rd
75%
6th
73%
17th
65%
25th
61%
26th
54%
19th
54%
7th
51%
25th
43%
2nd
56%
6th
62%
27th
Highest
Mean
96%
26th
93%
15th
96%
20th
95%
21st
93%
19th
94%
3rd
95%
9th
92%
29th
86%
4th
84%
29th
90%
26th
87%
12th
Averages Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Mean 82% 84% 88% 85% 80% 81% 78% 71% 68% 62% 72% 73%
Mean
Minimum
69% 71% 79% 75% 65% 67% 62% 50% 47% 41% 52% 52%
Mean
Maximum
92% 93% 94% 93% 91% 92% 89% 90% 87% 85% 89% 90%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 17/18 73%
93%
84%
Spring 2018 59%
90%
76%
Summer 2018 47%
87%
68%
Autumn 2017 64%
92%
80%

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 Oct 31-day Year 365-day
Least
Humid
50%
Ending 9th May 2016
60%
May 2011
75%
2011
58%
Ending 6th May 2011
73%
2016
71%
Ending 17th Jul 2017
Most
Humid
96%
Ending 27th Nov 2014
92%
Dec 2009
85%
2013
93%
Ending 20th Jan 2010
77%
2010
79%
Ending 7th Apr 2010
Lowest
Mean
Daily-Min
32%
Ending 19th Jul 2013
41%
Jul 2018
59%
2011
37%
Ending 21st Jul 2018
57%
2015
56%
Ending 11th Jul 2015
Highest
Mean
Daily-Min
92%
Ending 27th Nov 2014
84%
Dec 2009
70%
2013
86%
Ending 20th Jan 2010
62%
2010
62%
Ending 20th Jun 2018
Lowest
Mean
Daily-Max
73%
Ending 25th Apr 2017
76%
Apr 2017
82%
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
95%
2012
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 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 41%
Jul 2018
76%
Apr 2017
60%
May 2011
2 42%
Jul 2013
79%
Jun 2017
60%
Apr 2017
3 42%
May 2011
80%
May 2011
61%
Jun 2015
4 42%
Jun 2015
80%
Apr 2011
61%
Jul 2013
5 43%
Jul 2014
80%
Apr 2011
62%
Apr 2011
6 43%
Jul 2015
80%
Jun 2015
62%
Jul 2018
7 44%
Jun 2014
80%
Jul 2017
63%
Jul 2015
8 44%
Apr 2015
81%
Jul 2010
63%
Jul 2010
9 44%
May 2015
82%
Jul 2015
63%
Jun 2017
10 44%
Apr 2011
82%
Dec 2016
64%
May 2015


Most Humid Days in October
Rank Min Max Mean
1 98%
Day 22, 2012
98%
Day 7, 2009
98%
Day 22, 2012
2 98%
Day 23, 2012
98%
Day 10, 2009
98%
Day 23, 2012
3 96%
Day 13, 2014
98%
Day 22, 2009
96%
Day 13, 2014
4 95%
Day 15, 2018
98%
Day 23, 2009
96%
Day 21, 2012
5 94%
Day 21, 2012
98%
Day 24, 2009
96%
Day 15, 2018
Least Humid Days in October
Rank Min Max Mean
1 35%
Day 3, 2011
69%
Day 6, 2016
59%
Day 3, 2011
2 36%
Day 2, 2011
73%
Day 10, 2013
60%
Day 6, 2016
3 40%
Day 1, 2011
75%
Day 26, 2014
63%
Day 2, 2011
4 42%
Day 18, 2011
77%
Day 22, 2011
64%
Day 22, 2011
5 43%
Day 6, 2011
78%
Day 3, 2011
64%
Day 5, 2016

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.