Linen trousers are the one warm weather purchase I'd defend without hesitation, because nothing else lets air move the way linen does, and that matters more than the creasing everyone warns you about. You accept the creases as the price of being comfortable in a heatwave, the same way you accept a slightly battered hat.
These come into their own from late spring through to the end of summer, on days too hot for anything structured, on long train journeys where you need to sit for hours without your legs feeling clammy, and on the kind of holiday where you'll wear the same three things on rotation. If you're buying your first pair, go for a straight leg in a mid weight linen rather than the thin, almost see through kind, and pick a neutral colour, a stone or a soft olive, because the pale ones show everything and the dark ones show the heat.
They sit well against a plain cotton top or a linen shirt left open over a vest, and they work equally hard under a loose blazer for anything that needs a bit more polish, or with flat sandals and nothing else when the day doesn't require effort. Where people come unstuck is the waist and the rise, buying a size based on the hip measurement and ending up with trousers that gape at the back, or going too fitted through the thigh because linen has almost no stretch to forgive a tight cut. Try them sitting down before you decide, because a rise that feels fine standing can dig in the moment you're in a chair for any length of time, and that's the fit problem nobody mentions on the label.
The fabric shrinks a touch in the wash, so buy with a little room rather than exact, and resist the tumble dryer unless you enjoy the look of trousers meant for someone four inches shorter. Washed properly and dried flat, a decent pair comes back season after season looking much as it did, slightly softer, a shade less structured, but not tired, even after being balled up in the bottom of a bag for a week. Tomorrow morning I'd put mine on with a plain white t-shirt and canvas trainers, and not think about them again until it was time to take them off.