Climbing Forecast › Flatirons › Third Flatiron

FLATIRONS · FOUNTAIN SANDSTONE

Third Flatiron weather & climbing conditions

Good — dry and climbable

Right now

Temp57°F
Wind9 mph
Gusts13 mph
Humidity48.5%
Rain 48hdry
Last rainNone recent

Assessment

No recent rain
Good friction temperature range for fountain-sandstone

7-day forecast

Scroll through each day — hourly detail is shown inline.

Today Saturday 10 October
Good
Temp32°F
Raindry
Wind9 mph
Gusts13 mph
Humidity49%
No recent rain
  • Fountain sandstone dries fast in the sun — adularia-cemented arkose behaves like granite, not desert sandstone
Time °F Rain Wind (mph) Gust Hum
06:00 — dry — — null%
14:00 — dry — — null%
Sun Sunday 11 October
Good
Temp68°F
Raindry
Wind5 mph
Gusts—
Humidity33%
No recent rain
  • Fountain sandstone dries fast in the sun — adularia-cemented arkose behaves like granite, not desert sandstone
Time °F Rain Wind (mph) Gust Hum
06:00 55° dry 7 — 55.3%
07:00 54° dry 7 — 57%
08:00 56° dry 7 — 54.6%
09:00 61° dry 5 — 47.6%
10:00 65° dry 4 — 37.4%
11:00 66° dry 3 — 35.7%
12:00 67° dry 4 — 33.7%
13:00 69° dry 7 — 31.3%
14:00 71° dry 7 — 29.5%
15:00 72° dry 6 — 29.9%
16:00 72° dry 6 — 30.3%
17:00 71° dry 6 — 31.1%
18:00 67° dry 5 — 38.4%
19:00 62° dry 7 — 45.3%
20:00 61° dry 9 — 46.3%
21:00 59° dry 8 — 49.5%
Mon Monday 12 October
Good
Temp73°F
Raindry
Wind11 mph
Gusts—
Humidity20%
No recent rain
  • Fountain sandstone dries fast in the sun — adularia-cemented arkose behaves like granite, not desert sandstone
Time °F Rain Wind (mph) Gust Hum
06:00 50° dry 11 — 52.7%
07:00 50° dry 11 — 51.9%
08:00 54° dry 11 — 44.8%
09:00 63° dry 12 — 32.7%
10:00 68° dry 13 — 25.6%
11:00 71° dry 12 — 21.9%
12:00 74° dry 9 — 19.3%
13:00 75° dry 9 — 18.2%
14:00 76° dry 10 — 17.4%
15:00 74° dry 11 — 19.6%
16:00 74° dry 11 — 18.8%
17:00 72° dry 11 — 20.1%
18:00 68° dry 10 — 24.6%
19:00 64° dry 8 — 28.7%
20:00 60° dry 7 — 35.9%
21:00 60° dry 14 — 37.4%
Tue Tuesday 13 October
Good
Temp55°F
Rain0.01 in
Wind5 mph
Gusts—
Humidity66%
No recent rain
  • Good friction range for Fountain sandstone
  • Fountain sandstone dries fast in the sun — adularia-cemented arkose behaves like granite, not desert sandstone
Time °F Rain Wind (mph) Gust Hum
06:00 47° dry 6 — 86.2%
07:00 46° dry 4 — 85.4%
08:00 48° dry 4 — 84.6%
09:00 50° dry 3 — 80.3%
10:00 53° dry 4 — 72.3%
11:00 56° dry 6 — 63.9%
12:00 57° 0.01 in 6 — 62.2%
18:00 56° dry 4 — 68.7%
Wed Wednesday 14 October
Poor
Temp45°F
Rain0.1 in
Wind6 mph
Gusts—
Humidity95%
3.2mm rain forecastHumidity 95% — potential fog
  • Good friction range for Fountain sandstone
  • Sun-exposed Fountain walls dry within hours; shaded lower walls take longer
  • Damp air — small edges may feel greasy
Time °F Rain Wind (mph) Gust Hum
06:00 46° 0.05 in 5 — 98.1%
12:00 45° 0.03 in 6 — 95.3%
18:00 44° 0.03 in 4 — 97.1%
Thu Thursday 15 October
Poor
Temp45°F
Rain0.06 in
Wind5 mph
Gusts—
Humidity87%
1.5mm rain forecast
  • Good friction range for Fountain sandstone
  • Sun-exposed Fountain walls dry within hours; shaded lower walls take longer
  • Damp air — small edges may feel greasy
Time °F Rain Wind (mph) Gust Hum
06:00 38° 0.00 in 2 — 96.7%
12:00 45° 0.01 in 5 — 86.5%
18:00 45° 0.04 in 6 — 94.7%
Fri Friday 16 October
Poor
Temp45°F
Rain0.05 in
Wind4 mph
Gusts—
Humidity95%
1.3mm rain forecastHumidity 95% — potential fog
  • Good friction range for Fountain sandstone
  • Sun-exposed Fountain walls dry within hours; shaded lower walls take longer
  • Damp air — small edges may feel greasy
Time °F Rain Wind (mph) Gust Hum
06:00 43° 0.02 in 4 — 98.7%
12:00 45° dry 4 — 94.9%
18:00 48° dry 4 — 81%
Sat Saturday 17 October
Good
Temp59°F
Rain0.00 in
Wind4 mph
Gusts—
Humidity58%
Should be dry
  • Good friction range for Fountain sandstone
  • Fountain sandstone dries fast in the sun — adularia-cemented arkose behaves like granite, not desert sandstone
Time °F Rain Wind (mph) Gust Hum
06:00 39° dry 1 — 84.5%
12:00 59° dry 4 — 58.2%
18:00 56° dry 1 — 63%
Access
Boulder OSMP raptor closures typically run February 1 – July 31

About Third Flatiron

The Third Flatiron is the most iconic climbing formation in Colorado — a 1,300-foot east-facing tilted slab of Fountain Formation arkose rising above Chautauqua Park on the flank of Green Mountain, visible from every neighbourhood in Boulder. The Fountain Formation adularia-cemented arkose here is exceptionally hard — Denver Gazette's geology piece specifically credits the K-feldspar cement for the Flatirons' resistance — and the east aspect means sun from roughly 9am to 3pm before the wall goes into shade. on the Third — extended into August in some recent years; check bouldercolorado.gov/services/osmp-closures before travelling. Approach ~40 minutes from Chautauqua Park; the standard descent is a fixed rappel down the west face. Free public access, OSMP land.

Region
Flatirons
Rock type
Fountain sandstone
Aspect
east-facing
Altitude
6736 ft
Exposure
medium
Seepage
low

Other crags in this region

First Flatiron