The Complete Rainy-Day Running Guide: Shoes, Clothing, and Ground-Friction Adjustments

The 3 Physical Variables of Rainy-Day Running

1. Reduced Ground Friction

Friction coefficients change depending on the surface and how wet it is:

Surface Type	Dry μ	Slightly Wet μ	Soaked μ	Risk
Asphalt	0.8	0.6	0.5	Medium
Concrete	0.9	0.5	0.3	High
Tile	0.7	0.3	0.2	Very High
Wooden Boardwalk	0.8	0.4	0.2	Very High
Steel Manhole Cover	0.6	0.2	0.1	Very High
Painted Crosswalk	0.7	0.3	0.15	Very High

Bottom line: The most dangerous surface in the rain isn’t asphalt — it’s tile, manhole covers, crosswalk paint, and wooden boardwalks.

2. Accelerated Heat Loss

How fast your body loses core heat in the rain:

• Dry conditions, 15°C: heat loss of 1°C/hour
• Light rain, 15°C: heat loss of 2°C/hour
• Heavy rain, 15°C: heat loss of 3-4°C/hour
• Heavy rain + wind (10 m/s): heat loss of 5-6°C/hour

Once core temperature drops below 36°C, you enter the hypothermia risk zone, and your pace will noticeably slow down.

3. Reduced Visibility

Visible distance in the rain:

• Drizzle: visibility 200m+ (minor impact)
• Moderate rain: visibility 100-200m
• Heavy rain: visibility 50-100m
• Downpour: visibility < 50m (running not recommended)

Choosing Running Shoes

Rainy-Day Essential: High-Drainage Running Shoes

Key criteria:

• Upper: Breathable mesh is better than dense synthetic leather (letting water drain out matters more than blocking it)
• Midsole: EVA absorbs less water; supercritical foam materials drain faster
• Outsole tread: Deeper than 4mm, multi-directional grooves, diamond or hexagonal traction patterns
• Insole: Removable, quick-drying insoles

Recommended Types

Shoe Type	Suitable Scenario	Examples
Trail running shoes	Trails, dirt roads in the rain	Salomon, Hoka Speedgoat
Road training shoes (with slip-resistant outsole)	Urban rain running	Asics GT-2000, Brooks Adrenaline
Racing shoes	Rain-day races	Nike Vaporfly water-resistant version, Saucony Endorphin

Shoes to Avoid

• Pure white-soled running shoes (poor traction)
• Carbon-plated racing shoes (most models get slippery in the rain)
• Old shoes with more than 800 km on them
• Pure trail running spikes (they slip on paved roads)

Choosing Clothing

The 3-Layer Rainy-Day System

Base layer (next-to-skin, moisture-wicking):

• Material: polyester, polypropylene
• Avoid: pure cotton (poor insulation once wet, causes chafing)
• Length: covers below the waist

Mid layer (insulating, can be skipped in summer):

• Material: thin wool, brushed fleece wicking shirts
• Thickness: 100-150 g/m²
• Not needed for summer rain

Outer layer (waterproof, breathable):

• Material: Gore-Tex, eVent, or a brand’s proprietary waterproofing tech
• Breathability: RET < 13 (lower is more breathable)
• Zippers: waterproof zippers (YKK AquaGuard)
• Ventilation: underarm and back zip vents

Layering by Temperature in the Rain

Temperature	Base Layer	Mid Layer	Outer Layer
> 25°C	Moisture-wicking short sleeve	—	None (or a light sun cap)
20-25°C	Moisture-wicking short sleeve	—	Lightweight windbreaker/rain jacket (< 100g)
15-20°C	Moisture-wicking long sleeve	—	Rain jacket + waterproof cap
10-15°C	Moisture-wicking long sleeve	Thin fleece	Waterproof jacket + waterproof cap + gloves
< 10°C	Thick insulating long sleeve	Medium fleece	Waterproof jacket + insulated cap + waterproof gloves

Small Items Easily Overlooked

• Waterproof cap: keeps rain out of your eyes and improves visibility
• Water-resistant running socks: wool blends (e.g. 80% Merino wool)
• Waterproof gloves: protects fingers on cold rainy runs
• Calf sleeves: protects calves and guards against small stones
• Hooded rain jacket: adjustable fit around the head

Pace Adjustments

Pace Adjustment by Rainfall Level

The following is based on a 5:00/km marathon-pace baseline:

Rainfall	Pace Adjustment	Heart Rate Change	Risk Level
Drizzle	+0 sec/km	No change	Low
Light rain (< 5mm/hr)	+5 sec/km	+2 bpm	Low
Moderate rain (5-15mm/hr)	+15 sec/km	+5 bpm	Medium
Heavy rain (15-30mm/hr)	+25 sec/km	+8 bpm	High
Downpour (> 30mm/hr)	Running not recommended	—	Very High

Fine-Tuning Your Running Form

In the rain you should:

• Shorten stride by 5-10%: reduces slipping
• Increase cadence slightly by 3-5 bpm: compensates for the shorter stride
• Lower your center of gravity slightly: bend the knees a bit more
• Land mid-foot: avoid heel-striking first (it’s more prone to slipping)
• Avoid sharp turns: start slowing down 20m before any bend

Route Selection

Preferred Rainy-Day Routes

1. School PU track (good drainage, stable surface) ★★★★★
2. Indoor treadmill ★★★★★
3. Riverside asphalt path (avoid boardwalk sections) ★★★★
4. Park trails ★★★
5. Regular sidewalks ★★ (avoid tiled sections)

Routes to Avoid in the Rain

• Mountain trails (mudslides, falling rocks, poor visibility)
• Wooden boardwalks (extremely slippery)
• Sections with heavy tiling
• Long unsheltered bridges (wind and rain combine)
• City alleys with many manhole covers

4 Techniques for Rainy-Day Training

1. Before the Run

• Check the weather app for rainfall amount and trend
• Bring your phone and an emergency contact card
• Tell your family your route and expected return time
• Pack a compact rain jacket in a waist pack

2. During the Run

• If your shoes get wet, don’t stop to take them off — keep running
• If your body temperature drops sharply, find shelter immediately or speed up to get home
• If there’s lightning, stop immediately and find indoor shelter
• If you fall, check for a sprain before continuing

3. After the Run

• Change into dry clothes within 30 minutes (to avoid catching a cold)
• Stuff running shoes with newspaper and place them in a shaded, ventilated area (don’t use a clothes dryer — it damages the adhesive)
• Wash apparel in cold water and avoid the dryer (it breaks down the waterproof coating)
• Drink something warm or have hot soup to help restore core temperature

4. Gear Maintenance

• Reapply DWR waterproofing spray to your rain jacket every 5 washes
• Wipe down running shoes and apply shoe polish (for leather surfaces) every couple of weeks
• Check your watch’s water-resistance rating (5 ATM or higher is suitable for rain running)

When You Should Skip the Run

Do not run under the following conditions:

• Thunderstorms (even if the lightning seems distant)
• Downpours (rainfall > 30mm/hr)
• An approaching typhoon
• Standing water on the road deeper than 5 cm
• Visibility < 50m
• Feels-like temperature < 5°C
• Icy surfaces (even if they look dry)

Conclusion: Rainy-Day Training Is an Advanced Skill

Rainy-day training isn’t a “badge of toughness” — it’s preparation for races that might have rain. If your target race could realistically see rain (such as the New Taipei Marathon, Tokyo Marathon, or Taichung Marathon), rainy-day training is a necessary skill.

But if it’s just everyday training, switching to an indoor treadmill when it pours is completely fine. Smart runners know when to push through and when to back off.

Related Reading

• The Complete Guide to Running in Rain and Cold Weather: Gear, Safety, and Training Adjustments
• The Pace Difference Between Rainy and Sunny Runs: 5 Variables Behind That 20 sec/km Slowdown
• Weather Strategy for Road Races: Adjusting for Rain, Heat, and Strong Wind
• Triathlon Rain-Gear Checklist: Race-Day Rain Preparation and Backup Gear