When I was a kid trick-or-treating in the 1980s, it felt like it rained (or snowed) EVERY HALLOWEEN - and it nearly did.
The coldest HIGH temp for Halloween was a chilly 29* in 1917.
As for high temps making it to the 70s in Cedar Rapids, it has only achieved that figure just 13 times on Halloween, most recently in 2008, according to data from the Iowa Environmental Mesonet. The high temperatures on Halloween have only reached into the 80s just THREE times since 1893, most recently in 1968. All-time record high (since 1893) for Halloween in Cedar Rapids is 86* set in 1950.