Mittens are perhaps the warmest way to protect your hands when the weather is cold, wet, or a combination of both. Mittens often feel warmer than gloves because they allow skin-on-skin contact between your fingers. Consider a hybrid mitten (lobster mitt) if you need the dexterity of a glove and the warmth of a mitten. When deciding which pair of mittens to buy, consider their waterproof protection, insulation, and the overall design. Mittens with gauntlet cuffs slip over your jacket sleeves to prevent snow from sneaking up the arms. Mittens with under-the-cuff gauntlets offer a slimmer profile fit but provide less protection when it comes to stopping snow, wind, and wetness from slipping up inside your sleeves.
Wetness can be more dangerous to your hands than the cold. Look for mittens that use a waterproof breathable technology like Gore-Tex or at least a shell fabric with a waterproof coating like DWR.
Insulation traps heat to keep your hands warmer longer. Down insulation offers the best warmth-to-weight ratio, while synthetic insulation usually performs better in wet weather. Because it dries quickly, synthetic insulation is less affected by wet weather or sweat.
A gauntlet-style cuff keeps wetness and cold air from creeping up the sleeve of your jacket. This design can feel bulky to some, so if you want a sleeker fit, look for a glove with a slim fit that slips under your jacket cuff.