Weather moves faster than bikes. Reading the sky—and knowing when to shelter—separates uncomfortable rides from dangerous ones.
Cloud Types That Matter
Cumulus (puffy white): Fair weather. Watch for vertical growth—towers building upward indicate afternoon thunderstorm development.
Cumulonimbus (anvil-shaped): Thunderstorm in progress or imminent. The classic anvil top means mature storm capable of lightning, heavy rain, hail, and severe winds. Seek shelter immediately.
Stratus (gray blanket): Steady rain likely but rarely dangerous. Expect wet but manageable conditions.
Lenticular (lens-shaped): High winds aloft, often appearing near mountains. Ground-level winds may follow.
The 30/30 Rule
Count seconds between lightning flash and thunder. Divide by 5 for approximate miles. Under 30 seconds (6 miles)? Seek shelter. Stay sheltered until 30 minutes after the last thunder.
On open roads, any lightning visible is too close. Bikes are exposed targets. Get off the bike and away from it.
Mountain Weather Patterns
Mountains create their own weather. Standard pattern in summer:
- Morning: Clear, cool, stable
- Midday: Cumulus building over peaks
- Afternoon: Thunderstorms likely, especially over high terrain
- Evening: Storms dissipate, clearing overnight
Plan to be off exposed passes by early afternoon. Start climbing at dawn to summit before storms develop.
Wind Reading
Changing wind direction: Weather system approaching. West-to-east wind shifts often precede frontal passages.
Sudden calm after wind: In storm conditions, this may indicate the storm’s edge passing—or the brief calm before the most intense part arrives.
Increasing wind speed: System strengthening. Strong wind with temperature drop typically means cold front.
When to Stop
Pride kills cyclists. There’s no route worth risking lightning strikes or hypothermia. Conditions that warrant stopping:
- Visible lightning within 10 miles
- Hail of any size
- Winds making bike control difficult
- Visibility under 100 yards
- Uncontrollable shivering (early hypothermia)
Developing Instincts
After enough exposure, you’ll sense weather changes before they’re visible. The humidity shift before rain. The pressure drop that brings headaches. The particular stillness before storms.
Pay attention. Your body knows more than you realize.
