Dry Conditions and Low Humidity: April 14-16, 2009

The first half of April, 2009 was dry across much of central and southern Minnesota. One noticeable feature of the dryness was the low dew point temperatures and corresponding relative humidity during the middle of the month. The lowest relative humidity seen in the Twin Cities was 12% at 1pm April 14. The temperature was 61 and the dew point temperature was 8. How does this compare to other low humidity events in the past?

Days with hourly reports of relative humidity values of less than or equal to 15% are fairly rare. Looking at the Twin Cities hourly record back to 1945 (see below) there were only 57 days with low humidity of 15% or lower. These low humidity days are most common in April and early May. The driest of them all was April 22, 1953 at 5pm with a relative humidity of just 10%.

Twin Cities International Airport
Hours with Relative Humidity Less Than or Equal to 15%

yyyymmdd       hr(CST)      RH(%)

19460509       13           15

19520415       14           14
19520415       15           14
19520415       16           13
19520415       17           14
19520415       18           15

19520428       17           15
19520428       18           15

19530422       17           10

19531001       16           15
19531001       17           15

19540520       15           14
19540520       16           15

19551026       16           15

19570422       17           14

19570430       14           14
19570430       15           12
19570430       16           13
19570430       17           13
19570430       18           14
19570430       19           15

19570505       17           15
19570505       18           14

19570506       17           14
19570506       18           14
19570506       19           15

19580418       15           14
19580418       16           15

19580515       14           15
19580515       16           13
19580515       17           14

19580516       14           15
19580516       15           14
19580516       16           14
19580516       17           15

19590326       12           15
19590326       15           15

19590327       14           15
19590327       16           14
19590327       17           14
19590327       18           15

19590410       17           15

19590413       15           14
19590413       16           13

19590422       14           15
19590422       15           14

19590516       17           13
19590516       18           13

19640416       17           15
19640416       18           14

19710513       16           15

19730515       16           15
19730515       17           15
19730515       18           15

19761102       15           11
19761102       16           14

19800419       20           14
19800419       21           15

19800420       13           15
19800420       14           15
19800420       15           15

19800421       15           15
19800421       16           15
19800421       17           14

19800428       15           15
19800428       16           14
19800428       17           13
19800428       18           15

19800503       13           15
19800503       14           15
19800503       15           14
19800503       16           15
19800503       17           15
19800503       18           15

19800504       13           15
19800504       14           13
19800504       15           14
19800504       16           15
19800504       17           14
19800504       18           15
19800504       19           14

19810519       17           15

19810520       12           15

19840421       16           14
19840421       17           15
19840421       19           15

19870406       15           12

19870407       14           15
19870407       15           15
19870407       16           13
19870407       17           14
19870407       18           13
19870407       19           15

19870408       15           15
19870408       16           15

19870429       13           15
19870429       15           13
19870429       16           11
19870429       17           11
19870429       18           14
19870429       19           14

19870506       15           15
19870507       16           15

19880418       17           15
19880418       18           15

19880419       15           15
19880419       16           14
19880419       17           15
19880419       18           15
19880419       19           15

19880504       17           12
19880504       18           12
19880504       19           15
19880504       20           15
19880504       22           15

19880505       15           14
19880505       16           14
19880505       17           14

19880506       15           15

19890512       20           14
19890512       24           14

19890513       1            15

19900414       15           15
19900414       16           15

19920507       19           15
19920509       15           15

19930404       12           15
19930404       13           13
19930404       15           13
19930404       16           15
19930404       17           15

19930420       18           15

19960322       13           15
19960322       14           14

19991025       15           13
19991025       16           11
19991025       17           12
19991025       18           12

20030408       15           14
20030408       17           13
20030408       18           13
20030408       19           13

20040402       14           14
20040402       15           14
20040402       16           14
20040402       17           14
20040402       18           13
20040402       19           14

20050504       12           15
20050504       13           15
20050504       14           15
20050504       15           15
20050504       16           15

20060417       16           15

20070517       19           14
20070517       20           14

20090412       15           15
20090412       16           15