yeah how do think us on the chilly side keep our water safe for fish hehe
it is correct the bacteria (nitrosamonas and nitrobacter)do favour the warmer temperatures.
but it is still fine to cycle without a heater indeed.
it takes roughly 2 to 3 weeks longer than heated water though.
so you will have your heater by then anyway,get that cycle started early and you wont be waiting as long