Or you could introduce an aircon unit that's what I would / and have done in the past... There absolute pennies and work fantastic ...
I bought a second hand domestic 4.5KW A/C unit a few years back to help combat the temperatures in the summer, luckily I was working in the main bedroom which was on the north side of the building so it never got direct sunlight on it. After buying the unit (which weighed a ton) I realised i could not use it in the tent because, a) it was to big to get in there, and 
if i had of been able to get it in there I had no way of filtering the extracted air from it without pumping out "smelly" air. The result was that I used it to cool the ambient temperature of the room extracting the hot air out through the ceiling to the loft space. If you have used tents then you know that they are like having massive radiators in the room. As i was able to extract out through the ceiling and draw fresh air in from outside of the building for both of the tents so I had a slight advantage, but cooling the ambient temperature of the room made a big difference. Unfortunately when i bought the unit all of the refrigerant in it had leaked. A "friendly" engineer was recommended but he had problems re-charging it and ended up putting two new valves on it trying to charge it. It did pump out very cold air for a couple of months but it continued to leak and lost all of the gas. I still have it and my car mechanic says he should be able to recharge it for me but i don't want to use that much electric for A/C on top of what i am already consuming.
UPDATE:
Wednesday I went shopping and picked up some 50mm key rings and zinc screw hooks. This will allow me to gain about 250m and raise the lights as high as possible doing away with the cable ties and EZ rollers. Temperatures have been pretty constant at 29.5C to 30.5C and the humidity have been between 30-35%, I would still like the humidity to be higher at between 45-55% and i have some ideas on how to raise it passively. I had a lazy day Thursday as my back was playing up so didn't do anything other than feed the plants and refill the humidifier. Tomorrow I plan to reposition the lights at the same time raising them to as high as possible because I will lose so much headroom when i re-pot the plants in the 78 liter planters. After that I have some work to do in the kitchen fitting another light under the shelf I fitted earlier in the week. Then I have to refit my 1.2 x 1.2 tent in the dining room so I can bring in my tomato and scotch bonnet pepper plants that are in grow bags inside to ripen them as the weather will just rot the fruit on the vine. After that is complete hopefully i can go out and pick up some Perlite so i can re-pot what I need to over the weekend. I will try and take some photos so you can see what I am up to.
