2140 degrees farenhiet. Thats' WAY hotter than a bonfire. Remember that it's molten ROCK. This isn't like an oven, which only goes up to a thousand or so. Human skin combusts at 130 degrees farenheit. Keep in mind that all this heat can radiate pretty far. You will start to burn within a few feet.
You would pass out from heat stroke if you got closer than a few feet. Your skin would start to burn very quickly, not in a few minutes. The lava flows people watch tend to have cooled down quite a bit since leaving the volcano.