Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 50%
Humidity Trend -1% /hr
24hr Mean Humidity 61%
Wet-Bulb Temperature 13.4 °C
Absolute Humidity 8.18 gm-3
Air Density 1215.31 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 47%
11:44
51%
17:19
Maximum 69%
07:30
88%
14:05
Mean 60%
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 (09-15)
Measure 7-day Month 31-day Year 365-day Overall May 24th May
Lowest
Min
30%
21st
30%
21st
30%
21st
27%
15th Apr
27%
15th Apr
22%
15th Jul 2013
26%
Day 2, 2013
32%
2010
Highest
Max
94%
18th
97%
14th
97%
15th
98%
4th Jan
98%
16th Feb
98%
6th Feb 2009
98%
Day 2, 2014
91%
2012
Highest
Min
51%
23rd
72%
14th
72%
14th
96%
4th Jan
96%
4th Jan
98%
23rd Dec 2009
91%
Day 28, 2014
73%
2013
Lowest
Max
69%
Today
69%
Today
69%
Today
69%
6th Mar
69%
Today
56%
20th Jul 2010
56%
Day 2, 2013
69%
2010
Lowest
Mean
55%
21st
52%
12th
52%
28th
48%
15th Apr
46%
3rd Jul
39%
2nd May 2013
39%
Day 2, 2013
51%
2011
Highest
Mean
70%
23rd
86%
14th
86%
14th
97%
4th Jan
98%
26th Nov
98%
23rd Dec 2009
96%
Day 28, 2014
83%
2013
Averages                
Mean 63% 65% 65% 72% 75% 76% 67% 65%
Mean
Minimum
44% 44% 44% 55% 57% 59% 47% 47%
Mean
Maximum
81% 84% 85% 88% 89% 89% 85% 80%

Past Year Monthly Averages and Extremes (May 2014 - April 2015)
Extremes May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Lowest
Min
31%
19th
33%
22nd
28%
3rd
33%
3rd
42%
8th
46%
7th
51%
1st
53%
10th
48%
10th
41%
24th
28%
12th
27%
15th
Highest
Max
98%
2nd
95%
30th
95%
9th
96%
26th
97%
16th
98%
5th
98%
4th
97%
31st
98%
4th
98%
3rd
96%
1st
96%
26th
Highest
Min
91%
28th
66%
19th
82%
11th
81%
26th
92%
20th
96%
13th
96%
16th
86%
17th
96%
4th
86%
14th
75%
19th
71%
4th
Lowest
Max
71%
23rd
69%
21st
70%
3rd
74%
3rd
86%
25th
75%
26th
88%
11th
76%
23rd
76%
11th
75%
2nd
69%
6th
70%
15th
Lowest
Mean
54%
5th
51%
21st
46%
3rd
52%
3rd
70%
8th
69%
26th
76%
1st
71%
10th
69%
16th
66%
24th
50%
12th
48%
15th
Highest
Mean
96%
28th
78%
4th
90%
11th
92%
26th
94%
20th
96%
13th
98%
26th
91%
30th
97%
4th
93%
16th
85%
9th
87%
3rd
Averages May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Mean 69% 65% 65% 68% 79% 83% 90% 83% 81% 80% 69% 64%
Mean
Minimum
49% 44% 43% 46% 59% 68% 81% 72% 67% 65% 51% 44%
Mean
Maximum
88% 86% 86% 86% 94% 94% 96% 92% 92% 91% 87% 85%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 14/15 68%
92%
81%
Spring 2014 48%
87%
68%
Summer 2014 44%
86%
66%
Autumn 2014 69%
94%
84%

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
60%
May 2011
60%
2011
58%
Ending 6th May 2011
72%
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
42%
Jul 2013
42%
2011
40%
Ending 15th May 2011
55%
2015
57%
Ending 4th Apr 2012
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
80%
May 2011
80%
2011
77%
Ending 7th May 2011
88%
2011
87%
Ending 1st Apr 2012
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%
15th Jul 2013
3 26%
19th Apr 2011
61%
28th Mar 2012
43%
20th Jul 2010
4 26%
2nd May 2013
62%
6th Jan 2009
43%
28th Mar 2012
5 27%
25th May 2011
63%
21st Feb 2013
45%
17th Jul 2013
6 27%
28th Mar 2012
64%
31st Jan 2009
46%
25th May 2011
7 27%
15th Apr 2015
65%
2nd Feb 2012
46%
3rd Jul 2014
8 28%
28th Jun 2010
65%
27th May 2013
47%
28th Jun 2010
9 28%
23rd Jul 2012
66%
19th Jul 2010
47%
19th Jul 2010
10 28%
3rd Jul 2014
66%
21st Apr 2011
47%
4th Jul 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 42%
Jul 2013
80%
May 2011
60%
May 2011
2 42%
May 2011
80%
Apr 2011
61%
Jul 2013
3 43%
Jul 2014
81%
Jul 2010
62%
Apr 2011
4 44%
Jun 2014
82%
Jul 2013
63%
Jul 2010
5 44%
Apr 2015
83%
Jun 2010
64%
Apr 2015
6 44%
Apr 2011
84%
Jun 2013
65%
Jun 2014
7 44%
Aug 2013
84%
Jul 2011
65%
Current
8 44%
Current
84%
Apr 2010
65%
Jul 2014
9 45%
Jul 2010
84%
Current
66%
Apr 2013
10 45%
Apr 2013
85%
May 2013
66%
Apr 2010


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
46%
Day 25, 2011
3 29%
Day 3, 2011
66%
Day 1, 2011
47%
Day 27, 2013
4 29%
Day 26, 2012
67%
Day 20, 2011
48%
Day 6, 2011
5 29%
Day 27, 2012
69%
Day 24, 2010
49%
Day 27, 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.