The main volcanic danger is not eruptions: these are predicted by the geophysical study services following seismic and other detectable activity. The main danger is fog and temperature differences.
The volcano is a high altitude environment 2600 m. When there are no clouds, the sun is really scorching - there are no trees or other opportunities for finding shade, and the light reverberates on the rocks. Sunscreen is then strongly advised. Yet, clouds and fog may come in very quickly; then, the temperature falls and it is impossible to find one's way if one has strayed from the marked path.
Always carry a flashlight, drinking water and layered clothing, including a rain jacket. Wear hiking shoes.
Get the weather forecast before going to the volcano, and do not hesitate to postpone the trip should bad weathered be announced - if the danger is not sufficient to convince you, just think you won't see much up there with everything cloudy and rainy.
Carry a turned off GSM phone for emergencies. Note that not all the volcano is covered by GSM.
Certain areas are marked as "off-limits" by the authorities - typically because of unstable ground. Respect them.
