If you’ve ever hit the water in summer with your usual trout or steelhead setup and noticed that your casting feels off — or maybe your fly line is wearing out faster than expected there’s a good chance it could be you aren't using the right line.

We get a lot of questions about this in the shop, and it all comes down to a topic that doesn’t get nearly enough attention: fly line coatings and temperature compatibility.

Fly lines are made from plastics with varying hardnesses, designed to perform differently depending on water and air temperature — not unlike summer vs. winter tires.

Here in Southern Ontario, we fish everything from icy winter flows to scorching mid-summer lakes. That’s a swing of over 40°C (or 100°F) — and a standard fly line isn’t designed to handle that entire range.

What Happens When You Use a Cold-Water Line in Hot Weather?

Most trout or steelhead lines are designed for cold water, usually under 70°F (21°C). But when you bring those same lines into summer conditions, several issues start popping up:

Heat causes the plastic coating of a cold-water line to soften. That makes it more vulnerable to wear — especially as it moves through the guides, picks up grit, or drags through weeds. A soft line burns out quicker, and we see it happen all the time.

As the coating softens, it becomes tacky. That means friction through the guides, lower line speed, and less casting distance. Your casts might feel sluggish or “sticky,” even if your form is dialed.

When line loses structure, it becomes too limp to shoot cleanly — especially when stripped into coils at your feet. You’ll see more tangles and knots, which wastes time and costs fish.

On the flip side, tropical lines, which are made for temps over 80°F (27°C), get too stiff in cooler weather. They coil up, become brittle, and don’t lay out cleanly — especially in shoulder-season or spring conditions.

This is why matching your fly line to the water temperature is just as important as choosing the right rod or reel. And fortunately, brands are making it easier than ever.

We might not live in the tropics, but in July and August, the water can get hot — especially in stillwaters or rivers with less flow. In these conditions, warm-water lines are your best friend. A great developement is that companies are now producing the same taper of line in multiple coatings, meaning you can seamlessly switch between the seasons without adjusting to the casting dynamics of a new line. As an example, the SA Infinity Taper comes in 3 different options:

This is the same taper across all three lines, so if you love how your line casts and feels, you don’t need to change your technique — just swap the coating to match the weather.

Not Sure What Line Is Right for You?

Whether you’re a die-hard trout angler looking to fish ethically through the summer, a bass fanatic, or prepping for a warm-weather fly-in, we’re happy to help.

Drop by the shop, give us a call, or shoot us a message — we’ll help you dial in the right line to make the most of your season.

See you on the water!