Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 81%
Humidity Trend +0% /hr
24hr Mean Humidity 79%
Wet-Bulb Temperature 15.4 °C
Absolute Humidity 12.05 gm-3
Air Density 1228.00 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 71%
10:39
61%
17:30
Maximum 84%
03:19
84%
08:10
Mean 79%
74%
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 (09-16)
Measure 7-day Month 31-day Year 365-day Overall Sep 27th Sep
Lowest
Min
44%
23rd
36%
13th
34%
30th
22%
18th Jul
22%
18th Jul
22%
15th Jul 2013
24%
Day 8, 2012
51%
2015
Highest
Max
85%
21st
95%
5th
95%
5th
95%
6th Jan
97%
2nd Nov
98%
6th Feb 2009
98%
Day 15, 2009
98%
2010
Highest
Min
71%
Today
83%
10th
83%
10th
92%
6th Jan
95%
2nd Nov
98%
23rd Dec 2009
92%
Day 20, 2014
80%
2010
Lowest
Max
81%
24th
80%
14th
80%
14th
67%
5th May
67%
14th Aug
56%
20th Jul 2010
73%
Day 1, 2013
84%
Today
Lowest
Mean
63%
23rd
62%
13th
60%
30th
41%
5th May
41%
5th May
39%
2nd May 2013
54%
Day 8, 2012
72%
2015
Highest
Mean
79%
Today
93%
10th
93%
10th
93%
10th Sep
96%
2nd Nov
98%
23rd Dec 2009
96%
Day 13, 2013
91%
2010
Averages                
Mean 70% 75% 74% 72% 75% 75% 76% 80%
Mean
Minimum
55% 59% 58% 54% 59% 58% 57% 62%
Mean
Maximum
84% 87% 87% 86% 87% 89% 90% 92%

Past Year Monthly Averages and Extremes (September 2015 - August 2016)
Extremes Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
Lowest
Min
37%
10th
47%
1st
55%
21st
53%
30th
48%
30th
42%
28th
30%
14th
32%
27th
27%
8th
32%
6th
22%
18th
29%
26th
Highest
Max
95%
22nd
96%
25th
97%
2nd
94%
13th
95%
6th
92%
13th
94%
10th
91%
15th
94%
11th
93%
20th
91%
13th
93%
2nd
Highest
Min
82%
16th
87%
29th
95%
2nd
89%
15th
92%
6th
83%
13th
83%
9th
67%
15th
80%
11th
88%
1st
62%
27th
88%
2nd
Lowest
Max
83%
12th
84%
12th
82%
18th
73%
5th
83%
15th
74%
2nd
77%
31st
73%
18th
67%
5th
77%
7th
68%
7th
67%
14th
Lowest
Mean
65%
12th
70%
1st
69%
21st
68%
5th
72%
30th
61%
27th
60%
31st
54%
13th
41%
5th
58%
10th
55%
6th
51%
14th
Highest
Mean
91%
22nd
92%
21st
96%
2nd
91%
15th
93%
6th
88%
13th
89%
9th
86%
15th
88%
11th
90%
1st
80%
12th
89%
2nd
Averages Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
Mean 77% 83% 84% 81% 84% 74% 74% 66% 66% 76% 66% 67%
Mean
Minimum
56% 69% 75% 71% 74% 57% 54% 45% 47% 59% 46% 47%
Mean
Maximum
91% 92% 90% 89% 90% 86% 88% 86% 83% 88% 83% 85%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 15/16 67%
88%
80%
Spring 2016 49%
86%
69%
Summer 2016 51%
85%
70%
Autumn 2015 67%
91%
81%

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
72%
2016
73%
Ending 4th Apr 2012
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
54%
2016
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 20th Jul 2013
80%
May 2011
87%
2012
77%
Ending 7th May 2011
86%
2016
87%
Ending 9th May 2016
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 22%
15th Jul 2013
56%
20th Jul 2010
39%
2nd May 2013
2 22%
18th Jul 2016
56%
2nd May 2013
41%
5th May 2016
3 24%
8th Sep 2012
61%
28th Mar 2012
41%
15th Jul 2013
4 24%
30th Jun 2015
62%
6th Jan 2009
43%
20th Jul 2010
5 24%
10th Jul 2015
63%
21st Feb 2013
43%
28th Mar 2012
6 24%
19th Jul 2015
64%
31st Jan 2009
44%
10th Jul 2015
7 26%
19th Apr 2011
65%
2nd Feb 2012
44%
1st Jul 2015
8 26%
2nd May 2013
65%
27th May 2013
45%
17th Jul 2013
9 27%
25th May 2011
65%
1st Jul 2015
45%
30th Jun 2015
10 27%
28th Mar 2012
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
80%
May 2011
60%
May 2011
2 42%
May 2011
80%
Apr 2011
61%
Jun 2015
3 42%
Jun 2015
80%
Jun 2015
61%
Jul 2013
4 43%
Jul 2014
81%
Jul 2010
62%
Apr 2011
5 43%
Jul 2015
82%
Jul 2015
63%
Jul 2015
6 44%
Jun 2014
82%
Jul 2013
63%
Jul 2010
7 44%
Apr 2015
83%
Jul 2016
64%
May 2015
8 44%
May 2015
83%
Jun 2010
64%
Apr 2015
9 44%
Apr 2011
83%
May 2016
65%
Jun 2014
10 44%
Aug 2013
84%
Jun 2013
65%
Jul 2014


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.