Climate Overview:
The climate in the Mountain West and High Plains is perhaps more varied than any other climate in the United States and Canada. Elevation dictates much of the climate in this region. High-elevation areas experience cold winters and short summers. The high plains are milder but windy, and the low-elevation river valley areas are milder and wetter. Rainfall averages from under 10 to 20 inches annually in the deserts of Utah and up to 40 to 50 inches in the mountains and valleys of Colorado. While all areas within this region experience snowfall, the amount and severity depend on elevation. The high mountain regions have snow on the ground from October to June, while the more temperate valleys and plains typically do not retain snow very long after a snow event. The Rocky Mountain area features extremes and rapid fluctuations of temperature, wind, and light intensity. Spring can happen suddenly, but so can a late spring snowfall. Summers are often sunny, hot, dry, and short. The high plains regions will experience steady wind in spring and summer, with a high average of sunny days. With the exception of the high-mountain regions, exterior concrete work is preformed year-round with adjustments based on weather.

Regions of high elevation (above 7,000 feet)

High Mountains Winter

Climate (Mid October – Early April): This region experiences long winters. The first substantial snowfall typically arrives by the end of October, and snow is usually not gone until May or June. Because of the high average of sunny days and the sun's intensity at high altitudes, south-facing areas lose snow significantly faster than those on the north side or in shadowed areas. During the winter, exterior concrete work typically stops, with the exception of jobs that can afford tenting or other means of raising the ground and air temperatures above freezing. Standard concrete blankets may not be enough in high mountain regions to perform cold-weather concreting. Because of typical deep snow cover, rocky soil, and sunny days, the ground only freezes to an average depth of a few inches in mountain regions. This can be deeper on north-facing slopes. Lower-elevation river valleys in the region may see significantly less snow and milder temperatures, allowing for more favorable exterior concreting conditions.

Mix Designs: Cold-weather concrete mix designs are mandatory for all exterior concrete placed in this region during the winter. The primary considerations include chemical set accelerators to help the concrete set faster and air-entrainment admixtures to help with freeze-thaw conditions. Air entrainment should be mandatory in all exterior concrete placed in this region. Straight concrete mixes can also be used, as they tend to set faster than hybrid mixes. Taking the temperature of the concrete when it arrives at the jobsite is important to ensure it is not too cold and prone to freezing before curing.

Placement and Curing Practices: Cold-weather concreting practices are mandatory for all exterior concrete placed in this region during the winter. Due to extensive freeze-thaw conditions, this region is prone to spalling and scaling concrete. Proper mix design, placement, and curing are crucial for long-term concrete durability. The primary considerations include blankets for heat retention as well as the possibility of tenting in very cold conditions. Curing concrete in these regions usually requires the use of solvent-based cure or cure-and-seal chemicals to avoid freezing. The ready-mix supplier should be consulted far in advance of the concrete pour, since some plants in high-mountain areas shut down for the winter. Also, some states have road restrictions that may create a logistical issue in delivering concrete. Additional travel time can affect concrete performance, especially in very cold temperatures. With terrain in the mountain regions often playing a factor, pumping concrete becomes more common. Proper planning and communication are keys to a successful winter pour.

Special Equipment:

  • Sprayers to apply curing compounds
  • Ground heaters if the ground is frozen prior to the pour
  • Concrete pumps to speed the placement of concrete in cold conditions
  • Curing blankets and non-water-based curing compounds
  • Tenting
  • Proper cold-weather attire for crews pouring and finishing the concrete

High Mountains Spring

Climate (April – June): High-mountain regions typically see a short, wet spring. Often winter transitions directly to summer. Snowfall can occur at any time during the spring months, with wide temperature swings. If pouring exterior concrete during March through May, both winter and spring conditions may exist in a 24- hour period, so plan accordingly and check the extended forecast before pouring.

Mix Designs: Reference High Mountains Winter

Placement and Curing Practices: Reference High Mountains Winter.

Special Equipment: Reference High Mountains Winter

High Mountains Summer

Climate (June – August): Warm days and cool nights are the norm for high-mountain summers. High-intensity sunshine with very low humidity is the norm. Temperatures are mild to cool during the summer season. Late afternoon thunderstorms are common, so exterior concrete pours should be planned for the morning, with rain protection mandatory after the job is complete. Most exterior concrete work takes place during the summer in the high-mountain region.

Mix Designs: Dealing with low humidity and intense sunshine can require the use of admixtures to extend the set time. Hydration stabilizers and water reducers are commonly used to extend the working life of the concrete without affecting performance. Air-entrainment admixtures should be mandatory in all exterior concrete placed in this region.

Placement and Curing Practices: Because of the low humidity in high-mountain regions, rapid surface hydration is common and can be compounded by the intense sunshine and any wind that may be present. It is always a good idea to have a surface evaporative control chemical on hand. The use of curing compounds or cure-and-seal chemicals is highly recommended to minimize shrinkage cracking. These cures need to be applied as soon as possible after finishing is complete to aid in moisture retention. Due to exposure of the hardened concrete to freeze-thaw conditions in winter, it is prone to spalling and scaling. Proper water content and finishing are critical for long-term durability.

Special Equipment: Plastic sheeting to protect concrete from sudden rain showers; sprayers to apply curing compounds and surface evaporative control chemicals.

High Mountains Fall

Climate (Late August – October): As with spring, this season is short and sometimes nonexistent. Snow can start falling in late August or early September, so any exterior concrete work poured during this season should plan for sudden cold weather. The day time temperatures are typically mild, with cold nights. Cold weather protection overnight becomes more important the deeper into the fall season you pour. Scheduling new exterior concrete work can be difficult, since concrete suppliers and installers are typically busy finishing as much work as possible before winter arrives.

Mix Designs: Reference both High Mountains Summer and Winter since this season can have elements of both climates.

Placement and Curing Practices: Reference both High Mountains Summer and Winter since this season can have elements of both climates.

Special Equipment: Reference both High Mountains Summer and Winter since this season can have elements of both climates.

Arid regions above 3,000 feet

High Plains Winter

Climate (December – March): Winters are generally mild, with average temperatures in the low to mid 40s. Winter precipitation is typically snow, with the heaviest snow occurring later in the winter. North-facing slopes and shaded areas will tend to retain snow for longer periods. The ground does not typically freeze hard or deep in these regions. Exterior concrete placement takes place year-round, with short stoppages for inclement weather or cold temperatures occurring periodically throughout the season.

Mix Designs: Cold-weather concrete mix designs are typically used in these regions, but can be replaced with standard mixes, weather permitting. Primary considerations include accelerators for rapid set (calcium chloride accelerators for standard gray concrete and non-chloride-based accelerators for colored concrete). Straight cement mixes are also used to aid in a faster set time. Taking the temperature of the concrete when it arrives at the jobsite is important to ensure it is not too cold and prone to freezing before curing.

Placement and Curing Practices: Cold-weather concreting practices will be dictated by the weather conditions on the day of the pour, which can range from cold weather to fair weather. The primary consideration is the use of blankets for heat retention. Curing concrete in these regions usually requires solvent-based curing compounds or cure-and-seal chemicals to avoid freezing. Due to extensive freeze-thaw conditions, this region is prone to spalling and scaling concrete. Proper mix design, placement, and curing are crucial for long-term concrete durability. The ready-mix supplier should be consulted far in advance of the concrete pour, since some states have road restrictions limiting vehicle weights allowed on the roads, which may create a logistical issue in delivering concrete. Additional travel time can affect concrete performance, especially in very cold temperatures. Proper planning and communication are keys to a successful winter pour.

Special Equipment: Pouring exterior concrete in the high plains regions in winter typically requires no additional or special equipment. The current weather conditions will dictate any special needs, which may include ground heaters if the ground is frozen prior to the pour, curing blankets, tenting of the pour area, sprayers for applying curing compounds, and cold-weather attire for crews pouring and finishing the concrete.

High Plains Spring

Climate (March – May): This region typically sees a wet and windy spring. Temperatures can swing drastically, with 30 F to 40 F changes in a 24-hour period not uncommon. Very windy conditions can exist, especially in foot hill areas and flat plains regions. In some areas, March and April are the heaviest snow months. If pouring exterior concrete during March though May, both winter and spring conditions may exist, so plan accordingly and check the extended forecast before pouring.

Mix Designs: Reference High Plains Winter.

Placement and Curing Practices: Due to high winds, using surface evaporative retarders along with proper curing chemicals is recommended.

Special Equipment: Reference High Plains Winter.

High Plains Summer

Climate (June – August): Hot days and cool nights are the norm for high plains summers. High-intensity sunshine with very low humidity is the norm. Daytime temperatures can be very warm, with late afternoon thunderstorms and some severe storms common. These storms tend to be more prevalent in early summer. Exterior concrete pours should be planned for the morning, with rain protection mandatory after the job is complete.

Mix Designs: Dealing with low humidity and intense sunshine can require the use of admixtures to extend the set time. Hydration stabilizers and water reducers are commonly used to extend the working life of the concrete without affecting performance. The use of fly ash is also common to help slow set time. Air-entrainment admixtures should be mandatory in all exterior concrete placed in this region.

Placement and Curing Practices: Because of the low humidity in this region, rapid surface hydration is common and can be compounded by the intense sunshine and any wind that may be present. It is always a good idea to have a surface evaporative control chemical on hand. The use of curing compounds or cure-and-seal chemicals is highly recommended to minimize shrinkage cracking. Morning placement of concrete is also common to avoid the heat of the day and afternoon thunderstorms. Pumping concrete for larger pours is also common, to speed the delivery of the concrete to the jobsite in hot weather. Proper water content and finishing are critical for long-term durability.

Special Equipment: Plastic sheeting to protect concrete from sudden rain showers; sprayers to apply curing compounds and surface evaporative control chemicals; concrete pump to help speed concrete placement on larger jobs.

High Plains Fall

Climate (September – November): Moderate temperatures with little precipitation make for good concrete placing conditions. A sudden cold front or snow storm can arrive as early as September, but cold weather is usually not a factor until December. Concrete can typically be placed at any time of the day, and cold weather protection may be needed at night later in the season. Scheduling new exterior concrete work in this region in the fall can be difficult, since concrete suppliers and installers are typically busy finishing as much work as possible before winter arrives.

Mix Designs: Reference high plains summer.

Placement and Curing Practices: Reference high plains summer.

Special Equipment: Reference high plains summer.

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