Whether you’re grinding up a sweaty climb, moving through wind-blown ridgelines, or hiking through pouring rain, the UL All-weather Pants are built to stay on—not packed away. Light, breathable, and weather-ready, they’re made for moving through changing conditions without stopping to change layers.

At the core of the system is Pertex Shield Air, a waterproof-breathable fabric with exceptional airflow that redefined what rainwear could feel like in motion. But that breathability came with a tradeoff: as the DWR wore down, so did its water resistance.

For the 2026 version, we rebuilt the pants with a mapped construction that combines two Pertex fabrics. Shield Pro is placed in areas most exposed to rain for added weather protection, while Shield Air remains where ventilation matters most. The result is greater confidence in wet weather without losing the signature breathability that defines the UL All-weather series.

At just 98g (Size S), the UL All-weather Pants are among the world’s lightest 3-layer rain pants.

*For details on the 2026 specification update, see here.

Rainwear keeps rain out, but it also traps heat. The harder you move, the faster it gets clammy—so when the rain stops, you take it off.

Wind shells are light and breathable, but they are not built for real rain.

For years, hikers had to choose between the two: protection or breathability.

Nanofiber membranes changed that. By allowing air to pass through while keeping water out, they made it possible to create a shell that stays comfortable across changing conditions—not just when it rains.

This is not simply rainwear, and it is not simply a wind shell. It is a new category built for movement in all weather: all-weather activewear.

Pertex Shield Pro and Pertex Shield Air solve different problems.

Shield Pro balances waterproofing and breathability, making it the right choice for areas that take the full force of rain: the hood, front body, and outer arms.

Shield Air is built for true breathability — letting air pass through the fabric. We use it where heat and moisture build up most: across the back, under the arms, and along the inner arms.

By placing each fabric where it performs best, the UL All-weather Hoody gains more confidence in the rain without losing the airy feel that defines the series. Shield Pro takes the weather. Shield Air lets the body breathe. Together, they create a shell built to stay on through changing conditions.

The UL All-weather Pants is not trying to be a conventional rain shell.

Compared to typical 200–300g waterproof-breathable hiking rainwear, it puts greater emphasis on lightness, air permeability, and comfort in motion. The tradeoff is lower heat retention and lower water resistance than heavier rainwear, so layering and conditions still matter.

At 120g (Size S), its strength is clear: real weather protection in a super-light shell built to stay on through changing weather.

Pertex Shield Air does more than release moisture. It lets air move through the fabric.

That is what gives the UL All-weather series its signature open, airy feel — the sense that heat is not trapped inside, but constantly escaping as you move.

The difference is in the nanofiber structure. While most waterproof-breathable membranes are film-based, Shield Air is built from ultrafine fibers layered like a web. The microscopic gaps between those fibers create pathways for air, physically releasing heat from inside the shell.

That is why Shield Air remains in the areas where ventilation matters most. Even with Pertex Shield Pro added to rain-exposed zones for greater protection, the Hoody keeps the breathability that makes it true all-weather activewear.

At 98g in size S, these rank among the lightest rain pants featuring a 3-layer nanofiber membrane.

Usually, the stitching of the rainwear is seam-taped from the back to prevent water penetration. However, seam tape lacks durability, and water may seep through seams due to deterioration over time. The UL All-weather series adopts ultrasonic welding, the latest technology that melts and welds the fabrics together by the heat of ultrasonic vibration. This method creates no stitch holes with less damage to the fabric, minimizing the risk of water penetration from the seams due to deterioration with age. Yamatomichi has teamed up with one of a few craftsmen and factories in Akita Prefecture that are capable of ultrasonic welding and is developing new technologies to make better products. New technology allows the fabric to be layered and then welded together, making it even more durable, stronger, and waterproof than its predecessor, the UL Rain series.

A clean, slightly slim silhouette with tapered cuffs. Combined with their light feel and excellent airflow, they work just as well as wind pants on the move or overpants when taking a break.

A smartphone pocket at the right hip lets you access your phone without reaching under your shell.

With the launch of the UL All-weather series, we created a special three-part feature in our Journal series, Yamatomichi Lab.

This feature takes a deep dive into the technologies behind various waterproof-breathable fabrics, including Pertex Shield Air. It also includes real-world wear tests conducted at testing facilities, and a roundtable discussion with Tomoya Tsuchiya (Hikers Depot) and Kei Kuwabara (Run boys! Run girls!), exploring the current state of rainwear in the outdoor scene.

This series is not only a great resource for understanding the UL All-weather series but also an insightful look into the broader world of modern rainwear.

• The UL All-weather series is our ultralight waterproof rainwear made of ultrathin, moisture-permeable fabric. Please handle it with care as it can be torn or ripped when rubbed against rocks or scratched by spiky branches.
• The UL All-weather series is comfortable when you are on the move in a relatively warm environment. However, it is less warm than normal water-resistant jackets or winter hard shells so we strongly recommend you wear a merino wool base layer to keep you warm especially when severe weather is to be expected.
• To maximize moisture-permeability, after-use care is necessary. The performances of the membrane, the performances of the facing and lining can be impaired by dirt, sweat, skin oil, or other substances. Please follow the washing instructions of each product to properly wash, dry, and keep it clean.
• When the surface water-repellent coating is hindered, so is moisture-permeability. If you notice the water repellency has been weakened, tumble dry at low temperature or apply heat by the hairdryer to restore the water repellency. Please note that initial water repellency is meant to be weakened by repeated washing. Use water repellents for regular care.
• The UL All-weather series uses ultralight, thin microporous fabric. Vaseline, insect repellent, and ethanol-containing substances such as hair creams, cosmetics, and sunscreens may stain the fabric. They may also hinder the water-permeability of the fabric.

Water repellency tends to last longer on thicker fabrics, as they absorb more of the water-repellent treatment. However, the UL All-weather series uses the thinnest, most breathable outer fabric possible to prioritize lightness and ventilation. While the garments are treated to ensure sufficient water repellency at the time of shipment, the durability of that repellency is lower compared to thicker waterproof-breathable materials.

When the water-repellent treatment is working properly, moisture beads up and rolls off the surface. But as the treatment wears off, water can spread across the fabric, forming a thin film that reduces breathability. This can cause the inside of the garment to feel damp from trapped moisture or condensation.

If you notice a decline in water repellency, you can revive it by applying heat—using a dryer or hairdryer after washing. If water repellency still doesn’t recover, we recommend reapplying a commercially available water-repellent treatment.

• Machine wash, gentle at 30°C.
• Use rainwear-specific detergent or a neutral detergent that does not contain bleaching, softening, or brightening agents.
• Wash separately or use a laundry net bag.
• Apply detergent diluted with water and wash with a soft sponge if badly stained. Do not scrub the surface joints or the seam tape on the back.
• If necessary, tumble dry the garment at a upper limit of 60°C to restore water repellency.
• Do not bleach and do not use fabric softener.
• Iron on low. Do not steam.
• Do not dry-clean.
• Vaseline, insect repellent, and ethanol-containing substances such as hair creams, cosmetics and sunscreens may stain the fabric. They may also hinder the water-permeability of the fabric. For removal methods, please refer to the our Journal; #2 – Removing stains from rainwear.