Choosing the right fly line can be a daunting task. Floating/sinking and weight are often the primary considerations in fly line selection and tend to get the most attention. Just as important, is using a fly line designed for the climate you’re fishing. So what is the difference between cold fly lines and tropical fly lines, and why does it matter?
Fly line specifications vary by manufacturer, so there are no definitive rules as to how they are categorized. Generally, fly lines are rated for three different temperature ranges: cold, temperate, and warm (tropical) water applications.
There are a few reasons why using a fly line designed for your climate is so important. A fly line will wear out more quickly in the wrong climate. The performance and enjoyability of using a line will also suffer. Given that a fly line is arguably the most important component of any fly fishing set up, proper line selection is critical.
Sometimes, a fly line will be rated for two different temperature ranges. A fly line may be rated for cold/temperate use for exmaple.
There is some overlap in the categorization between cold, and warm water lines. Different fly line manufacturers (and product lines) will have slightly different specifications. A line designed for cold/temperate climates will be the right choice for most fly anglers, but let’s dive into the specifics.
Cold Water Fly Lines
These fly lines work best in water temperatures below 10C (50F), and air temperatures below 15C (60F).
Cold-water species (such as trout, salmon, and char) are the most commonly targeted fish while fly fishing, so the majority of lines on the market are designed for cold water applications (or cold/temperate water hybrid).
Coldwater fly lines have a multi-filament (braided) core, which is more supple than that of those manufactured for warm water fishing.
Much of the marketing around fly lines is focused on the coating. Fly line coatings vary significantly, but in general cold water fly lines have more supple coating as well.
Examples of when a coldwater fly line is the best choice
- Chasing steelhead in great lake tribs.
- Most traditional salmon and trout fishing situations.
- Walleye fly fishing.
- Winter esox (pike and kin) fishing
- When targeting many rough fish species.
What happens if I use cold water fly lines in warm water?
The line loses stiffness and goes limp in high temperatures. This makes it harder to properly cast and turn over flies.
The fly line may also get a bit sticky if left out in the heat. Not only does this make the line not shoot well, it also makes it a bit unpleasant to handle. This can be minimized a bit by keeping the line wet if you just have a few days in a season that are on the warm side.
RIO Gold Fly Line (Amazon Link)
Temperate Water Fly Lines
These fly lines work best in water temperatures between 4C (40F) and 21C (70F), and air temperatures between 10C (50F) and 26C (80F).
Most temperate fly lines still use a braided core, but will differ from cold water fly lines in that the coating will be geared towards more temperate use.
Some examples of when a temperate fly line is the best choice.
- Most Smallmouth bass waters call for a temperate/warm water fly line.
- Largemouth bass fishing in Northern climates during shoulder seasons (fall/spring).
- Most carp fly fishing.
- Surf casting for striped bass.
- Most esox fishing applications
Warm Water Fly Lines
Also marketed as tropical fly lines, these are intended to be used in warm water temperatures.
These fly lines work best in water temperatures above 10C (50F), and air temperatures above 15C (60F).
Tropical fly lines have a core of monofilament, which is a stiffer material than the cores of cooler water fly lines. This allows the line to keep its rigidity at higher temperatures, where cooler water fly lines will cast like a wet noodle in hot climates.
The coating on warm water fly lines is also harder to withstand the warmer temperatures. A happy side effect of this, is that warm water fly lines are generally more durable than cold water lines.
Examples of when tropical fly line is the best choice:
- Fishing the flats for bonefish, snook, redfish, flounder, tarpon and other salterwater tropical game fish.
- Chasing peacock bass and in the canals of Flordia
- Proper jungle fishing. Chasing arowana, tropical snakeheads, Golden Dorado, and more. Very jealous of folks with this opportunity.
- Summer fishing for smallmouth.
What happens if I use warm water lines in cold water?
When used in cooler conditions, a tropical line is going to stiffen up and have alot of memory coming off the fly reel, it’ll coil. Stiff, coiled fly line will make line management frustrating and is more difficult to cast.
Since the line gets quite rigid when used in cold waters, you’ll also find it wears out more quickly. continuing to use warm water fly lines in cold water applications will cause the fly line coating to crack prematurely due to the rigidity.
RIO Fly Fishing Fly Line Smallmouth Bass (Amazon Link)
Tangent, What’s the difference between salt water and fresh water lines?
I’ve seen this question asked on a few fly fishing forums. Honestly, there isn’t an inherent difference in fly lines intended for saltwater vs freshwater. I wish that fly line manufacturers wouldn’t market lines as fresh vs saltwater, as it just confuses people. The deciding factors in line selection is weight, taper, and temperature weighting (which we’re covering here). “Saltwater” lines have aggressive tapers to turn over larger flies, and are (typically) designed with warmer water temperatures in mind.
Most saltwater fishing is done in tropical environments. Think permit, bonefish, tarpon, redfish, summer flounder, etc. So for most anglers fishing in the salt, temperate/tropical fly lines are the go to choice.
Fish exist in cold saltwater environments as well. The most popular of these (among fly anglers atleast) is striped bass, which would requires a fly line on the cold/temerate side.
A decision should be made based on the temperature of the water you’re fishing, regardless of whether it’s salt or freshwater.
Final Thoughts
Choose a fly line that suits the conditions you fish most of the time. If you’re an avid angler that fishes all season long, or travels alot to fish, then it makes sense to buy multiple lines. Don’t try to pick a line that’ll fish both winter steelhead and August Bass for example, get a dedicated line for each of these applications.
On the flip side, if you fish spring trout and summer bass in the same general area, you can likely find a line that’ll handle both situations.
Luckily, most fly line manufacturers state quite clearly if a line is intended for cold water or warm water applications. This makes choosing winter and summer fly lines easier.
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