Humidity & Temps in Spring & Summer for my Tarantula

I've noticed lately that the humidity level in my Chilean Rose Hair's tank has been jumping past the 70% mark a little! Last week for example, it was quite mild out & the humidity went up to 72%, then to 76% & then even as high as 79%, then I turned on the dehumidifier downstairs in the basement, & I noticed the humidity starting to drop a little. And just before when I last checked, the humidity was 69-70% & the temp was 74! I know that Chilean Rose's are from the deserts & not from the tropics & I've been keeping a very close eye on the humidity gauge making sure it doesn't jump up into the 80% range which is tropical, although I have this "Terrarium Animals from A-Z" Compass Guide book & it says for the Chilean Rose Hair that the atmospheric humidity should be 60-80%! And all other sources & books I've read says that's supposed to be 60-70%. Is there something I should be doing a little different since it's now springtime outside & it's going to start getting warmer out, esp. once summer hits? This is my first Tarantula that I've had since Jan; & I'm just trying to find out if the care conditions are a little different for a T in the spring/summer w/ the warm weather out?