i too run a couple L3 in my garage in hot summer weather. it can get wayyyy over 30c in there. i have the door propped and locked open about 6 inches for some air flow, but its not enough on hot days.
the cost of any sort of active cooling will negate the low profitability of these units, even box fans are electric motors that consume overpriced electricity (we have nasty daytime electric rates.)
i bought a couple of outlet boxes from aliexpress that turn on/off based on a thermostat setting.
https://www.aliexpress.com/item/Tempera ... 57670.html
the box has two temp setttings, one is the high temp you want it to automatically switch off, the other is the lower temp where you
wish it to switch back on. i switch one off at 45c and on at 38c , and two degrees lower for the other box.
hopefully one box switching off sooner is enough to avoid the second box from switching off so i still have some hashing power going on.
i place the temperature probes for the boxes as far away and slightly lower than my L3 units. (hot air rises)
could probably run these a few degrees warmer but i dont want to completely stress my L3s over time or have some garage junk spontaneously combust.
i have come home from work late afternoon to find they are switched off. yes, it gets over 45c in the garage when the outdoor temp is in the 30s
my units are slightly overclocked. underclocking may be an option to avoid overheating too -- but i dont want to keep reconfiguring the clock speed depending on time of day or outside weather. max hash or none.
ps: these thermostats can operate in reverse manner, ie: switch on at high temp and off at low temp, so they could be useful for running box fans only when necessary to save on electric costs.