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