Heat in the UK.....

The heat in my tent is just short of 100, I've got the whole thing open, extraction on, fan on - will it harm my week old seedlings? I'll be getting another fan tomorrow......

fans don't cool air just move it. your gonna need an ac with temps like that or you seedlings will fry.

lol, 30C "Heat wave" hahaha. dont have tent in direct sunlight, have good ventilation across the plants, and just make sure they have enough water. if ur having heat issues its probably because the area is too small, seedlings are particularly vulnerable to heat, i would also suggest removing any light hood you may have on ur light.

My temps get to about 90 ive got a 420 cfm exhaust fan and and ocsillating fan going. I find if I seal the room up it stays cooler than outside. So assuming you have an exhaust fan might wanna try that. Also an ac I cant afford one right now but thats an option. Ice would probably work well in a space the size of yours a few bags so you can rotate them.

Got my extraction on, one static fan strapped to the ceiling of the tent and now one oscillating over the plants...... Tents all sealed up, will check temp in half hour or so.... There's no more I can do - the tents not in direct sunlight and ac's not really an option (no where to put it....) Vegging at 16/8 under 400w mh which goes off at 1pm so it'll drop then anyway.......

If you can't use a 100$ 5,000 btu window a/c, you can get a 220$ 5,000 btu portable non window a/c. Will cost 2x as much as window version but it will allow you control on your temps during hot days.

change ur light cycle time, its on during the hottest part of the day...... make it so the night cycle starts at like 10am then starts up again at 6pm

It's on 7am-1pm at the moment....