- Ice openings and cracks in ice – the ice layer around them is weaker.
- Drifting blocks of ice – a block of ice can crumble fast. Often they attract the interest of children who try to ride them in spring, and can therefore get into danger of drowning.
- Ice is crackling – leave the ice immediately. When going on ice make sure that it can support the weight of a human, and avoid areas where the ice layer could be weaker.
- Moving around in darkness – there is a risk of losing your orientation and getting into an area where ice is weak. Moreover, you could miss possible cracks or holes.
- Light clothes – wind on a frozen body of water intensifies the feel of cold, and hypothermia kicks in faster.
- Different patches of colour can be observed on ice – different colours /tones of ice point to areas with different thickness of ice.
- Consumption of alcohol – alcohol creates a deceptive feeling of warmth, but does not prevent hypothermia.