Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 38%
Humidity Trend -8% /hr
24hr Mean Humidity 46%
Wet-Bulb Temperature 13.3 °C
Absolute Humidity 6.83 gm-3
Air Density 1193.27 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 39%
12:04
28%
15:07
Maximum 71%
07:18
67%
07:01
Mean 60%
41%
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 May 6th May
Lowest
Min
28%
5th
28%
5th
28%
5th
28%
5th May
24%
19th Jul
22%
15th Jul 2013
26%
Day 2, 2013
32%
2011
Highest
Max
88%
2nd
88%
2nd
91%
21st
95%
6th Jan
97%
2nd Nov
98%
6th Feb 2009
98%
Day 2, 2014
87%
2015
Highest
Min
53%
2nd
53%
2nd
67%
15th
92%
6th Jan
95%
2nd Nov
98%
23rd Dec 2009
91%
Day 28, 2014
55%
2012
Lowest
Max
67%
5th
67%
5th
67%
5th
67%
5th May
65%
11th Jul
56%
20th Jul 2010
56%
Day 2, 2013
70%
2011
Lowest
Mean
41%
5th
41%
5th
41%
5th
41%
5th May
41%
5th May
39%
2nd May 2013
39%
Day 2, 2013
48%
2011
Highest
Mean
74%
2nd
74%
2nd
86%
15th
93%
6th Jan
96%
2nd Nov
98%
23rd Dec 2009
96%
Day 28, 2014
73%
2015
Averages                
Mean 56% 56% 64% 74% 73% 75% 66% 62%
Mean
Minimum
37% 37% 43% 57% 57% 59% 46% 42%
Mean
Maximum
78% 78% 84% 87% 87% 89% 84% 80%

Past Year Monthly Averages and Extremes (May 2015 - April 2016)
Extremes May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Lowest
Min
30%
21st
24%
30th
24%
10th
30%
9th
37%
10th
47%
1st
55%
21st
53%
30th
48%
30th
42%
28th
30%
14th
32%
27th
Highest
Max
97%
14th
92%
2nd
92%
15th
93%
13th
95%
22nd
96%
25th
97%
2nd
94%
13th
95%
6th
92%
13th
94%
10th
91%
15th
Highest
Min
72%
14th
71%
13th
78%
13th
89%
31st
82%
16th
87%
29th
95%
2nd
89%
15th
92%
6th
83%
13th
83%
9th
67%
15th
Lowest
Max
73%
13th
69%
10th
65%
1st
71%
18th
83%
12th
84%
12th
82%
18th
73%
5th
83%
15th
74%
2nd
77%
31st
73%
18th
Lowest
Mean
49%
28th
45%
30th
44%
10th
54%
9th
65%
12th
70%
1st
69%
21st
68%
5th
72%
30th
61%
27th
60%
31st
54%
13th
Highest
Mean
86%
14th
81%
2nd
87%
13th
92%
31st
91%
22nd
92%
21st
96%
2nd
91%
15th
93%
6th
88%
13th
89%
9th
86%
15th
Averages May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Mean 64% 61% 63% 71% 77% 83% 84% 81% 84% 74% 74% 66%
Mean
Minimum
44% 42% 43% 52% 56% 69% 75% 71% 74% 57% 54% 45%
Mean
Maximum
84% 80% 82% 87% 91% 92% 90% 89% 90% 86% 88% 86%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 15/16 67%
88%
80%
Spring 2015 48%
86%
68%
Summer 2015 46%
83%
65%
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 May 31-day Year 365-day
Least
Humid
51%
Ending 19th Jul 2013
56%
Current
56%
Current
58%
Ending 6th May 2011
73%
2015
73%
Ending 4th Apr 2012
Most
Humid
96%
Ending 27th Nov 2014
92%
Dec 2009
72%
2012
93%
Ending 20th Jan 2010
77%
2010
79%
Ending 7th Apr 2010
Lowest
Mean
Daily-Min
32%
Ending 19th Jul 2013
37%
Current
37%
Current
40%
Ending 15th May 2011
57%
2015
56%
Ending 11th Jul 2015
Highest
Mean
Daily-Min
92%
Ending 27th Nov 2014
84%
Dec 2009
54%
2012
86%
Ending 20th Jan 2010
62%
2010
62%
Ending 8th Apr 2010
Lowest
Mean
Daily-Max
73%
Ending 20th Jul 2013
78%
Current
78%
Current
77%
Ending 7th May 2011
87%
2016
87%
Ending 29th Feb 2016
Highest
Mean
Daily-Max
98%
Ending 17th Jan 2010
97%
Dec 2009
88%
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 24%
8th Sep 2012
56%
2nd May 2013
41%
5th May 2016
3 24%
30th Jun 2015
61%
28th Mar 2012
41%
15th Jul 2013
4 24%
10th Jul 2015
62%
6th Jan 2009
43%
20th Jul 2010
5 24%
19th Jul 2015
63%
21st Feb 2013
43%
28th Mar 2012
6 26%
19th Apr 2011
64%
31st Jan 2009
44%
10th Jul 2015
7 26%
2nd May 2013
65%
2nd Feb 2012
44%
1st Jul 2015
8 27%
25th May 2011
65%
27th May 2013
45%
17th Jul 2013
9 27%
28th Mar 2012
65%
1st Jul 2015
45%
30th Jun 2015
10 27%
15th Apr 2015
65%
11th Jul 2015
46%
25th May 2011


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 37%
Current
78%
Current
56%
Current
2 42%
Jul 2013
80%
May 2011
60%
May 2011
3 42%
May 2011
80%
Apr 2011
61%
Jun 2015
4 42%
Jun 2015
80%
Jun 2015
61%
Jul 2013
5 43%
Jul 2014
81%
Jul 2010
62%
Apr 2011
6 43%
Jul 2015
82%
Jul 2015
63%
Jul 2015
7 44%
Jun 2014
82%
Jul 2013
63%
Jul 2010
8 44%
Apr 2015
83%
Jun 2010
64%
May 2015
9 44%
May 2015
84%
Jun 2013
64%
Apr 2015
10 44%
Apr 2011
84%
May 2015
65%
Jun 2014


Most Humid Days in May
Rank Min Max Mean
1 91%
Day 28, 2014
98%
Day 2, 2014
96%
Day 28, 2014
2 90%
Day 3, 2012
98%
Day 28, 2014
94%
Day 27, 2014
3 89%
Day 27, 2014
97%
Day 1, 2012
92%
Day 3, 2012
4 83%
Day 10, 2012
97%
Day 10, 2012
92%
Day 10, 2012
5 80%
Day 4, 2012
97%
Day 25, 2013
90%
Day 9, 2012
Least Humid Days in May
Rank Min Max Mean
1 26%
Day 2, 2013
56%
Day 2, 2013
39%
Day 2, 2013
2 27%
Day 25, 2011
65%
Day 27, 2013
41%
Day 5, 2016
3 28%
Day 5, 2016
66%
Day 1, 2011
46%
Day 25, 2011
4 29%
Day 3, 2011
67%
Day 20, 2011
47%
Day 27, 2013
5 29%
Day 26, 2012
67%
Day 5, 2016
48%
Day 6, 2011

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.