Excellently done for a class of people who somewhat already understand relative humidity. Speaking strictly from a presentation standpoint, there are a few things you could have done to make that very well done presentation even better.
Provide for a few "dramatic pauses" where your audience has time to think about what you have stated. Especially where you give calculations. Provide time for those in the audience who may not be following your calculationst to ask you to give them a way to better understand how you are getting to a calculated conclusion. Involve the audience a bit more.
Be certain to give a brief definition of technical terms that may not be completely understood by all in the audience. Just because we understand the terminology we are using does not mean that all of those we are talking to do.
You have a great capacity for memorizing data which allows you to be comfortable speaking without the constant use of notes. I would suggest joining a local Toastmaster's Club to hone the skills you already have. Toastmasters is a great way to try out new speaches on others while also working with a peer group that can evaluate your speaking in positive ways. Besides, the meetings are just fun.
All in all, a good training speech.