The heat is on!
 

Today we are supposed to hit 100. Yesterday, when we were at a mere 97, the temp in the greenhouse hit 103. I ran inside to get the aluminet sun shade, and almost immediately, the temperature dropped to 99. That's the good news.
The BAD news is that I already have a sun shade up (the kind you'd find at ACE or Lowe's), and with the aluminet, I'm afraid I won't have enough light for the cattleyas, much less the tomatoes. If the temperature in the greenhouse continues to rise, I'm likely to have fried plants.
Ideas?

I just invested in a mist king system. It arrived today so it will be going up over the weekend. Hopefully that will help.
My greenhouse has gone up to almost 40, so that's 110, tho recently it has been a bit cooler. Nothing died at that temp.

I have also heard of people buying swamp coolers (evaporative coolers) in places that are dry and hot like Arizona. Works as a cooling system that will add some humidity to the air. You need an opening to set it in so it sucks the dry air from outside, it is blown thru water saturated filters which cool the air and blow into the greenhouse.

Our swamp cooler has been running for months, silken. It goes on as soon as the temperature hits 85 in the greenhouse. We use them in our house, too, so we're very familiar with the concept. And the down side to the evap cooler is it doesn't do much once the rains come...though when that happens, the temperature usually drops a bit too.
It's the intensity of the sun that does it!

My mother has one in her home in New Mexico, works really well.

The swamp coolers work well in terms of bringing moist air into a dry place. We use it instead of an air conditioner until the monsoon. At that point, we have to switch to an air conditioner in the house. If it is humid outside, the swamp cooler just pushes the warm, hot air around. If it is, say, 110 with 12% humidity, the swamp cooler is terrific. Bring the humidity up to, say, 50% and the word "swamp" comes to mind!
We have a mister system that goes off every hour or so. That helps a little.
This is my first summer with the greenhouse, so every day is an experiment.

Me too. It's experiment all the way. If the misters work, I would like to get a nerpenthes, but there's no point if there isn't enough moisture around.

Sounds like you have it covered if you also have good air movement from fans in there. Short of installing the regular type of air con, (which would likely use lots of electricity and be a fairly costly approach), not sure what you could do.

I just stuck some containers of water in the freezer, thinking maybe if the air blows across ice, that might help.
We have an overhead vent that opens automatically when things heat up. And there are side louvers, plus the swamp cooler. At 2pm today, the prediction is 100 degrees with 8% humidity. Any moisture I gain is pretty much lost through the vents! This is going to be interesting!

Weird that you need an air conditioner with the swamp cooler, but I'm sure a greenhouse is way different. My mother does not have an air conditioner, just the swamp cooler and her house stays nice and cool.