Unusually Humid July in Rockford

...UNUSUALLY HUMID JULY IN ROCKFORD...

THE AVERAGE HOURLY DEWPOINT IN ROCKFORD DURING THE MONTH OF JULY
2011 WAS 70.01F...MAKING IT THE FIRST TIME DATING BACK TO 1980
THAT THE AVERAGE MONTHLY DEWPOINT IN JULY HAS BEEN OVER 70F.
DEWPOINT IS ACTUALLY A MUCH MORE ACCURATE REPRESENTATION OF HOW
HUMID THE AIR FEELS. HERE IS A RANKING OF THE AVERAGE DEWPOINTS
FOR THE MONTH OF JULY DATING BACK TO 1980...

1) 2011 - 70.0
2) 1999 - 68.1
3) 1983 - 67.1
4) 1987 - 67.0
5) 1980 - 66.6
6) 1986 - 66.5
7) 1982 - 66.0
8) 1993 - 65.3
9) 2006 - 65.4
10) 1995 - 65.3*
1998 - 65.3*
12) 2010 - 65.1
13) 1989 - 64.3*
2001 - 64.3*
2002 - 64.3*
16) 1994 - 64.2
17) 2004 - 64.1
18) 1981 - 63.7
19) 2003 - 63.6
20) 2000 - 63.4
21) 2008 - 63.0
22) 1996 - 62.0
23) 1997 - 61.7
24) 1990 - 61.6
25) 2005 - 61.3
26) 1985 - 61.1
27) 1991 - 60.8
28) 2007 - 60.6
29) 1984 - 60.4*
1988 - 60.4*
31) 1992 - 59.9
32) 2009 - 57.8

* DENOTES A TIE

SO WHY USE DEWPOINT RATHER THAN RELATIVE HUMIDITY TO RANK THE MOST
HUMID WEATHER AND WHAT IS THE DIFFERENCE BETWEEN THE TWO? THE
ANSWER IS THAT DEWPOINT IS AN ABSOLUTE MEASURE OF HOW MUCH
MOISTURE IS IN THE AIR...AND AIR CAN HOLD DIFFERING AMOUNT OF
MOISTURE DEPENDING ON THE TEMPERATURE. A GOOD ANALOGY IS TO THINK
OF HOW MUCH WATER IS IN A GLASS. TEMPERATURE IS A MEASURE OF HOW
BIG THE GLASS IS...RELATIVE HUMIDITY IS A MEASURE OF HOW FULL THAT
PARTICULAR SIZED GLASS IS...AND DEWPOINT IS A MEASUREMENT OF HOW
MUCH WATER IS IN THE GLASS.

HERE`S AN INTERESTING EXAMPLE...IF THE TEMPERATURE IS 95F AND THE
RELATIVE HUMIDITY IS 35%...THERE IS ACTUALLY MORE MOISTURE IN THE
AIR THAN IF THE TEMPERATURE WERE 68F AND THE RELATIVE HUMIDITY WAS
70 PERCENT. EVEN THOUGH THE RELATIVE HUMIDITY IS TWICE AS
HIGH...THE AIR CAN HOLD LESS MOISTURE AT 68F THAN AT 95F...SO
THERE IS ACTUALLY MORE MOISTURE IN THE AIR IN THE FIRST EXAMPLE.

DIFFERENT PEOPLE HAVE DIFFERENT TOLERANCE LEVELS FOR
HUMIDITY...BUT IN GENERAL HERE`S A BREAK DOWN FOR HOW DEWPOINTS
STACK UP.

60F - MOST PEOPLE CONSIDER HUMIDITY LEVEL COMFORTABLE
65F - SOME HUMIDITY IS NOTICEABLE...BUT STILL FAIRLY TOLERABLE
70F - MANY WOULD CONSIDER THIS TO BE FAIRLY HUMID
75F - VERY HUMID CONDITIONS...MOST PEOPLE CONSIDER IT UNCOMFORTABLE
80F - OPPRESSIVE HUMIDITY...TYPE OF AIR PEOPLE SAY CAN BE "CUT"

$$

IZZI


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