Humidity Type:
Difference?

Detailed Relative Humidity Data

Current
Measure Value
Relative Humidity 74%
Humidity Trend +0% /hr
24hr Mean Humidity 80%
Wet-Bulb Temperature 10.3 °C
Absolute Humidity 8.22 gm-3
Air Density 1246.19 gm-3
Recent Averages and Extremes
Measure Today Yesterday
Minimum 58%
15:30
82%
22:50
Maximum 96%
07:21
95%
08:14
Mean 80%
91%
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 (09-14)
Measure 7-day Month 31-day Year 365-day Overall Oct 25th Oct
Lowest
Min
47%
21st
46%
7th
46%
7th
28%
3rd Jul
28%
3rd Jul
22%
15th Jul 2013
35%
Day 3, 2011
56%
2010
Highest
Max
96%
Today
98%
5th
98%
13th
98%
5th Jan
98%
13th Oct
98%
6th Feb 2009
98%
Day 7, 2009
98%
2012
Highest
Min
82%
24th
96%
13th
96%
13th
96%
30th Jan
97%
12th Dec
98%
23rd Dec 2009
98%
Day 22, 2012
83%
2012
Lowest
Max
80%
22nd
80%
22nd
80%
22nd
66%
17th Apr
66%
17th Apr
56%
20th Jul 2010
73%
Day 10, 2013
87%
2010
Lowest
Mean
69%
22nd
69%
22nd
69%
22nd
46%
3rd Jul
46%
3rd Jul
39%
2nd May 2013
59%
Day 3, 2011
76%
2010
Highest
Mean
91%
24th
96%
13th
96%
13th
98%
30th Jan
98%
12th Dec
98%
23rd Dec 2009
98%
Day 22, 2012
93%
2012
Averages                
Mean 78% 83% 82% 73% 76% 75% 82% 82%
Mean
Minimum
63% 67% 66% 54% 58% 59% 67% 64%
Mean
Maximum
91% 94% 94% 90% 90% 89% 93% 93%

Past Year Monthly Averages and Extremes (October 2013 - September 2014)
Extremes Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Lowest
Min
52%
10th
54%
3rd
52%
5th
60%
23rd
46%
26th
32%
15th
34%
16th
31%
19th
33%
22nd
28%
3rd
33%
3rd
42%
8th
Highest
Max
98%
3rd
98%
4th
98%
10th
98%
5th
98%
1st
98%
1st
98%
21st
98%
2nd
95%
30th
95%
9th
96%
26th
97%
16th
Highest
Min
89%
3rd
95%
9th
97%
12th
96%
30th
84%
18th
77%
3rd
84%
7th
91%
28th
66%
19th
82%
11th
81%
26th
92%
20th
Lowest
Max
73%
10th
83%
30th
83%
3rd
86%
7th
76%
9th
69%
9th
66%
17th
71%
23rd
69%
21st
70%
3rd
74%
3rd
86%
25th
Lowest
Mean
66%
10th
71%
3rd
68%
6th
78%
9th
64%
9th
52%
9th
54%
17th
54%
5th
51%
21st
46%
3rd
52%
3rd
70%
8th
Highest
Mean
95%
16th
97%
9th
98%
12th
98%
30th
90%
19th
90%
3rd
93%
25th
96%
28th
78%
4th
90%
11th
92%
26th
94%
20th
Averages Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Mean 85% 85% 86% 88% 77% 71% 70% 69% 65% 65% 68% 79%
Mean
Minimum
70% 73% 76% 76% 60% 48% 50% 49% 44% 43% 46% 59%
Mean
Maximum
95% 95% 93% 96% 90% 89% 88% 88% 86% 86% 86% 94%

Past Year Seasonal Averages
Season Daily Min Daily Max Mean
Winter 13/14 71%
93%
84%
Spring 2014 49%
88%
70%
Summer 2014 44%
86%
66%
Autumn 2013 68%
94%
83%

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
51%
Ending 19th Jul 2013
60%
May 2011
75%
2011
58%
Ending 6th May 2011
73%
2014
73%
Ending 4th Apr 2012
Most
Humid
96%
Ending 19th Jan 2010
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
42%
Jul 2013
59%
2011
40%
Ending 15th May 2011
54%
2014
57%
Ending 4th Apr 2012
Highest
Mean
Daily-Min
91%
Ending 19th Jan 2010
84%
Dec 2009
70%
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
88%
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
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 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 28%
28th Jun 2010
65%
2nd Feb 2012
46%
3rd Jul 2014
8 28%
23rd Jul 2012
65%
27th May 2013
47%
28th Jun 2010
9 28%
3rd Jul 2014
66%
19th Jul 2010
47%
19th Jul 2010
10 29%
27th Jun 2010
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%
Feb 2010
90%
Jan 2010
3 80%
Dec 2010
96%
Jan 2014
89%
Feb 2010
4 79%
Nov 2011
95%
Jan 2010
89%
Nov 2011
5 77%
Dec 2012
95%
Oct 2012
88%
Dec 2010
6 77%
Nov 2010
95%
Nov 2011
88%
Jan 2014
7 76%
Jan 2013
95%
Oct 2013
87%
Dec 2012
8 76%
Jan 2011
95%
Nov 2009
87%
Nov 2010
9 76%
Jan 2014
95%
Nov 2009
87%
Jan 2013
10 76%
Dec 2013
94%
Nov 2012
86%
Nov 2009
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 2011
83%
Jun 2010
65%
Jun 2014
6 44%
Aug 2013
84%
Jun 2013
65%
Jul 2014
7 45%
Jul 2010
84%
Jul 2011
66%
Apr 2013
8 45%
Apr 2013
84%
Apr 2010
66%
Apr 2010
9 46%
May 2009
85%
May 2013
66%
Jul 2011
10 46%
Apr 2010
85%
May 2010
66%
Jun 2010


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 94%
Day 21, 2012
98%
Day 23, 2009
96%
Day 21, 2012
5 94%
Day 14, 2014
98%
Day 24, 2009
96%
Day 14, 2014
Least Humid Days in October
Rank Min Max Mean
1 35%
Day 3, 2011
73%
Day 10, 2013
59%
Day 3, 2011
2 36%
Day 2, 2011
77%
Day 22, 2011
63%
Day 2, 2011
3 40%
Day 1, 2011
78%
Day 3, 2011
64%
Day 22, 2011
4 42%
Day 18, 2011
78%
Day 7, 2011
65%
Day 6, 2011
5 43%
Day 6, 2011
79%
Day 21, 2011
66%
Day 18, 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.