Conditions to Expect Each Month

See also:

• Medano Creek Current and Forecast Flow
• Weather Information and Forecasts
• Medano Pass Primitive Road Conditions and Information

 

Snow falls about once per week in winter months.

NPS/Patrick Myers

January

January is usually the coldest month of the year, with average highs only in the teens to low thirties F and lows in the single digits to below zero F. Snow and blizzards are possible, though most days are sunny and calm. Roads are usually quickly cleared of snow. Snow falls on the dunes about once per week, but it typically melts off within a few days. Mountain hiking trails are under deep snow, but foothills trails may be packed down or have shallow snow. High-clearance 4WD vehicles can usually make it to Castle Creek Picnic Area along the Medano Pass Primitive Road, but the remainder of the road is closed for the winter season beyond that point. During this quiet season, elk and pronghorn are often seen in early morning or evening hours in the grasslands.

 

February is a dry month, but some snow falls on the dunes about once per week.

NPS/Patrick Myers

February

February has somewhat warmer temperatures than January, with average highs around 39 F and lows averaging 14 F. Snow and blizzards are possible, though most days are sunny and calm. Roads are usually cleared quickly of snow. Snow falls on the dunes about once per week, but it typically melts off within a day. Mountain hiking trails are under deep snow, but foothills trails may be packed down or have shallow snow. High-clearance 4WD vehicles can usually make it to Castle Creek Picnic Area along the Medano Pass Primitive Road, but the remainder of the road is closed for the winter season beyond that point. During this quiet season, elk and pronghorn are often seen in early morning or evening hours in the grasslands. Sandhill cranes begin to arrive in the San Luis Valley, and stay about 6-8 weeks.

 

March has volatile weather, and is the snowiest month of the year.

NPS/Patrick Myers

March

Plan on volatile weather in March. Some March mornings are sunny and calm, but most afternoons have high winds. Plan to experience the dunes in the morning if possible. Be prepared for occasional blizzard conditions and deep snow as well: March is the snowiest month of the year on average. Average highs are around 47 F and lows average 21 F. However, during winter storms temperatures may drop into the single digits, or in later March may reach a calm, sunny 60 degrees F. Roads are usually cleared quickly of snow. Snow falls on the dunes about once per week, but it typically melts off within a day. Mountain hiking trails are under very deep snow, but foothills trails may be packed down or have shallow snow. High-clearance 4WD vehicles can usually make it to Castle Creek Picnic Area along the Medano Pass Primitive Road, but the remainder of the road is still closed for the winter season beyond that point. Elk and pronghorn are sometimes seen in early morning or evening hours in the grasslands, but spring break traffic may move them farther away from roads. Medano Creek is still mostly frozen on the eastern side of the dunes, but will start trickling toward the main Dunes Parking area.

Spring break is on and the park becomes very busy if the weather is nice. The Dunes Parking Lot may even become full on busy weekends.

Elk and pronghorn may still be seen in the grasslands around dawn or dusk, but increasing traffic from spring break crowds tends to push them farther away out of sight. Sandhill cranes are in the valley in large numbers, with peak populations around the first week of March. By the end of March, most have migrated north.

The Milky Way is only visible in early morning hours during spring.

 

In April, Medano Creek first reaches the main Dunes Parking Area, but is still low in flow. High winds are common in spring, especially during afternoon hours.

NPS/Patrick Myers

April

Like March, April has volatile weather and often blustery conditions. Though the dunes don't get too hot on April afternoons, wind is common. Plan to experience the dunes in the morning to avoid the highest winds. April is the second snowiest month of the year on average. Typical highs are around 56 F and lows average 28 F. Roads are usually cleared quickly of snow. Snow falls on the dunes about once per week, but it typically melts off within a day. Mountain hiking trails are under very deep snow, but lower sections are melting out or dry. High-clearance 4WD vehicles can usually make it to Castle Creek Picnic Area along the Medano Pass Primitive Road. The remainder of the road may still be still closed for the winter season beyond that point, unless dry conditions permit opening it farther into the mountains. Elk and pronghorn might occasionally be seen in early morning or evening hours in the grasslands, but increasing traffic moves them farther away from roads. Trees are not yet leafed out. Medano Creek melts and moves father around the dunes, trickling down to the main Dunes Parking Area sometime in April. By late April, it may be up to a few inches deep. It's too cold still for most insects, but a few no-see-ums (tiny biting gnats) may be present on warm afternoons.

Piñon Flats Campground opens for the season each year around the beginning of April, and increasingly fills each night as the weather warms.

The Milky Way is only visible in early morning hours during spring.

 

Late May to early June is typically the peak flow of Medano Creek.

NPS/Patrick Myers

May

Late May is the average peak of Medano Creek's annual flow. While it is still springtime and winds may arise, especially in the afternoon, May temperatures are generally moderate, with highs in the 60s-70s F. However, snow is still possible in May at this elevation. Trees and bushes along the creek leaf out. There may be some "no-see-ums" (tiny biting gnats), but mosquitoes are rarely out in May. Late May and early June are the best opportunity to experience "surge flow", where waves up to about 20 inches (50 cm) high flow down across the sand. In wet years with good peak runoff, children can float down the waves on flat inflatable toys. Water comes out of the mountains cold, but warms up significantly when the sun shines on it as it spreads across the sand. Because of the creek's popularity, late May and early June weekends are extremely crowded, with long lines of traffic, overflowing parking lots, a crowded beach, and full campgrounds. If possible, plan your visit on a weekday this time of year.

The dunes start to get hot on later May afternoons, and could reach 150 degree F surface temperatures. Always plan your dunes time for early morning or evening to avoid burning sand, high winds, or thunderstorms with lightning.

The Medano Pass Primitive Road usually fully opens by late May. Mountain hiking trails are generally melted out up to about 9,500 feet (2,895m) by late May, but alpine lakes and trails are still under deep snow.

Piñon Flats Campground is typically full most nights in May, especially the latter half of May. Area campgrounds are also available.

The Milky Way is only visible past midnight during spring. Visit in late summer and early fall to see it high in the sky before midnight.

 

June brings decreasing water levels, but mosquitoes emerge from the shallow water around the second week of June.

NPS/Patrick Myers

June

June brings warmer temperatures for Medano Creek water play, with highs averaging 76 F, and lows around 45 F. Flow is at or close to peak in late May and early June. Because of the creek's popularity, late May and early June weekends are extremely crowded, with long lines of traffic, overflowing parking lots, a crowded beach, and full campgrounds. If possible, plan your visit on a weekday this time of year.

Creek flow decreases throughout June. By late June, the water level will usually be fairly low, averaging only about 1 inch (2 cm) or less. As the creek becomes low and warm around the second week of June, mosquitoes may emerge in large numbers. Mosquito season lasts about 4-7 weeks, depending on water levels. Move away from vegetation, to the far side of the creek to avoid the worst of the mosquitoes: they don't like open sand, but prefer to be near shady bushes and trees.

Sunny, calm conditions generally prevail except during storms. Sand temperatures may soar to 150 degrees F; always plan your dunes time for early morning or evening to avoid burned feet, heat exhaustion, or fatal lightning strikes. June is one of the drier months on average, but afternoon thunderstorms begin to develop. Alpine hiking trails (to Sand Creek Lakes, Medano Lake) are usually snow-free by mid-to-late June, but patches of snow remain above the lakes through July.

Piñon Flats Campground is full almost every night in summer months, especially in May and June. Area campgrounds are also available.

The Milky Way becomes visible earlier in the night, but in June it is typically around midnight before it's high enough to view clearly.

With lots of traffic, elk and pronghorn are usually far away from the main use area, but bighorn sheep are sometimes seen along the Medano Pass Primitive Road.

 

Medano Creek is reduced to a trickle during an average July, but wildflowers are at peak in the mountains above.

NPS/Patrick Myers

July

Medano Creek will begin to retreat back toward the mountains in July, drying up at the main visitor area near the Dunes Parking Lot. It will continue to gently flow (about 1 inch or 2 cm deep) along the eastern edge of the dunefield, near the Castle Creek Picnic Area along Medano Pass Primitive Road. With low water around for breeding, numerous mosquitoes are present from mid-June through July.

July is the warmest month at the park, with average highs in the low 80s F. Sunny, calm conditions generally prevail except during storms. Sand temperatures may soar to 150 degrees F; always plan your dunes time for early morning or evening to avoid burned feet, heat exhaustion, or fatal lightning strikes.

Afternoon thunderstorms are common in July and August, bringing wind, lightning and potentially heavy rain. They also bring up mountain wildflowers in Great Sand Dunes National Preserve.

The Milky Way becomes visible earlier in the night, and by late July it can be seen on clear moonless nights high in the sky about an hour and a half after sunset.

With lots of traffic, elk and pronghorn are usually far away from the main use area, but bighorn sheep are sometimes seen along the Medano Pass Primitive Road.

 

Millions of prairie sunflowers bloom in the grasslands and dunes during wet years. Peak bloom is the last two weeks of August.

NPS/Patrick Myers

August

August is the second warmest month at the park, with average highs in the upper 70s F and lows in the upper 40s F. Sunny, calm conditions generally prevail except during storms. Sand temperatures may still soar to 150 degrees F; always plan your dunes time for early morning or evening to avoid burned feet, heat exhaustion, or fatal lightning strikes.

Afternoon thunderstorms are common in July and August, bringing wind, lightning and potentially heavy rain. These rains bring mountain wildflowers in Great Sand Dunes National Preserve, and millions of prairie sunflowers in the dunes and grasslands. Sunflowers peak sometime the last two weeks of August.

Medano Creek's bed is usually dry at the main Dunes Parking Area during all of August. The mountains are barren of snow in late summer and early fall, but weather is generally pleasant, and mid-summer's mosquitoes are gone.

A clear moonless night in August is the best time to see the Milky Way high in the sky beginning an hour and a half after sunset.

With lots of traffic, elk and pronghorn are usually far away from the main use area, but bighorn sheep are sometimes seen along the Medano Pass Primitive Road.

 

Aspens peak with gold color in late September and early October above the dunes.

NPS/Patrick Myers

September

September has some of the best weather of the year, with an average high of 71 F and a low of 42 F. Sunny, calm conditions generally prevail except during storms. The dunes may still get very hot on early September afternoons, with surface temperatures reaching up to 150 degrees F.

Aspen trees turn gold throughout the month, beginning at the highest elevations. By late September to early October, lower aspen groves are at peak color. Snow showers begin to dust the mountains as temperatures cool. Access aspen groves by hiking trails or the Medano Pass Primitive Road.

A clear moonless night in September is still a good time to see the Milky Way beginning an hour and a half after sunset, but it gets increasingly lower in the sky through September and October.

As traffic decreases, elk and pronghorn may begin to come back into the grasslands in the main use area, especially around dawn and dusk. Bighorn sheep are sometimes seen along the Medano Pass Primitive Road.

 

Gold cottonwood trees peak in mid-October, and snow showers blanket the mountains as temperatures drop.

NPS/Patrick Myers

October

October brings chillier temperatures, but there are also some pleasant days, especially in the first half of the month. The average high is 60 F with lows around 32 F. Sunny, calm conditions generally prevail except during storms. The dunes have pleasant temperatures even in afternoon hours. The first snows typically fall on the dunes in late October.

Lower aspen groves are at peak gold in the first week or two of the month. Access aspen groves by hiking trails or the Medano Pass Primitive Road. By mid-October, cottonwood trees around the dunes are at peak deep gold color. Snow showers continue to dust the mountains as temperatures drop further.

If hiking in higher portions of the mountains in Great Sand Dunes National Preserve, keep in mind that hunting may be in season during your fall visit. Wear brighter colors, and be alert. Hunting is not permitted in any areas near the dunes. Most hikers in the mountains don't see any hunting activity taking place.

On a clear moonless night in October you can still see the Milky Way, but it is getting increasingly lower in the sky.

As traffic decreases, elk and pronghorn may begin to come back into the grasslands in the main use area, especially around dawn and dusk. Bighorn sheep are sometimes seen along the Medano Pass Primitive Road.

Sandhill cranes return to the valley, though the fall migration is more scattered with less available water in wetlands. Some cranes are typically present in various valley locations during October and the first half of November.

 

Elk are sometimes seen in early morning or evening in the grasslands around the dunes during quieter months.

NPS/Patrick Myers

November

November is early winter at this elevation, with highs averaging 46 F in the day and lows reaching 20 F at night. Winter storms are possible, but most days are sunny and calm, with pleasant afternoon conditions on the dunes. Elk and pronghorn start to be more often seen in the grasslands in early morning or evening as the park gets quieter. Bighorn sheep are sometimes seen along the Medano Pass Primitive Road, which stays open (weather permitting) until the end of hunting season, typically just after Thanksgiving weekend.

Visitation drops off considerably with colder temperatures, but Thanksgiving weekend can be somewhat busy.

If hiking in higher portions of the mountains in Great Sand Dunes National Preserve, keep in mind that hunting may be in season during your fall visit. Wear brighter colors, and be alert. Hunting is not permitted in any areas near the dunes. Most hikers in the mountains don't see hunting activity taking place.

Part of the Milky Way may be visible on clear moonless nights, but it is slipping lower and lower beneath the horizon.

Sandhill cranes begin to continue their migration southward, though there are usuallly a few cranes that stay around through November.

 

Snow frequently blankets and park and preserve in winter months, though the dunes tend to melt off within a day or two.

NPS/Patrick Myers

December

December brings heavier and longer-lasting snow along with much colder temperatures. The average high is 36 F with lows around 11 F, but sub-zero temperatures are possible. Snow falls about once per week on the dunes and mountains. Roads are usually quickly cleared of snow.

The park and preserve are generally quiet, except over the holidays. If fresh snow has fallen on the dunes, snow sledding or cross-country skiing are popular. The sand is firmer and partially frozen, making hiking easier. Afternoons on the dunes have the warmest temperatures.

Higher mountain trails are under snow, usually requiring gaiters and/or snowshoes. Lower foothills trails may be packed down or have shallow snow.

Elk and pronghorn are sometimes seen during early morning or evening in the grasslands.