A weather shelter tent used for extreme weather must have a priority on durability, strong weather protection, and possibly insulation or heat retention. Emergency Shelter Tent for Harsh Weather The following is an analysis of essential features and types:

Essential Features for Extreme Weather Shelter Tents:

Exceptional Waterproofing:
Very high hydrostatic head rating on both the rainfly (3000mm+) and floor (5000mm+).
Both the rainfly and floor completely taped seams.
Outer fabric's Durable Water Repellent (DWR) coating.
Excellent Wind Resistance:
Aerodynamic shape with a low profile.
Strong and flexible poles, preferably aluminum alloy.
Several guy-out points for safe anchoring.
Durability:
Heavy-duty, tear-resistant materials (e.g., ripstop nylon or polyester with high denier).
Reinforced stress areas.
Heavy-duty zippers (YKK or similar).
Insulation/Heat Retention:
Some emergency shelters utilize reflective Mylar material to maintain body heat.
Double-wall construction can provide improved insulation by trapping air between the inner and outer walls.
Snow skirts (draft collars) will keep snow and cold air out at ground level.
Ventilation (to control condensation):
Some ventilation is necessary even when it's cold in order to avoid moisture accumulation from body heat and breath. Check for rainfly vents.
Ease of Setup (in stressful conditions):
Quick and easy pitching architecture is essential. Pop-up or inflatables will be extremely quick to put up.
Portability and Weight:
Though strength is most important, the tent must also be portable in case it has to be transported with an emergency kit or carried on foot if a vehicle is unavailable.
Visibility:
Colorful colors such as orange or yellow will make the shelter more visible to rescue parties.
Types of Emergency Shelter Tents for Severe Weather:

Mylar Emergency Tents:
Light and compact, intended to reflect human body heat and offer basic wind and rain protection.
Usually single-layer and perhaps not as waterproof or long-lasting as other choices for extended harsh weather.
Tube Tents:
Lightweight, tube-shaped shelters usually constructed of polyethylene or Mylar.
Need to be suspended between two points. Packable and lightweight for emergency supplies.
Pop-Up Emergency Tents:
Pops up immediately. Can provide more room and longevity than Mylar tents.
Choose those constructed of waterproof materials.
Inflatable Emergency Tents
Utilizes air beams for support, enabling quick deployment and possibly enhanced stability.
May be more rugged and weather-resistant but can be pump-dependent.
4-Season Backpacking Tents:
Those which are built to withstand harsh weather conditions, such as heavy snowfall and heavy winds.
Constructed to be tough, heavy-duty poles, complete rainfly coverage, and commonly include snow skirts. May be heavier and costlier.
Survival or Bushcraft Tents:
Designed for durability in wilderness conditions and usually have sturdy materials and designs that can withstand different weather. 
Can have features such as stove jacks for warm shelters (use with extreme caution and ventilation).
Emergency Relief Tents (Large Scale):
Having disaster relief in mind, can accommodate several individuals. Constructed from tough, weather-resistant materials for temporary housing.
Recommendations for Severe Weather:

For truly extreme weather, particularly heavy rain, snow, and strong wind, a 4-season backpacking tent or a very tough survival/bushcraft tent will usually be the most reliable if portability does not limit the choice. In case extreme packability and weight are the absolutely highest priority for an emergency set, a good Mylar emergency tent or a well-built tube tent should at least be an option considered.

When selecting, first look for:

High water-resistance ratings and sealed seams.
Tough and stable structure.
Tear-resistant and long-lasting materials.
Sufficient room for the planned number of users.
Always read reviews and specifications thoroughly to make sure the tent is suitable for the particular harsh weather conditions you may be facing.