of most consecutive days of or above, during a period of 160 days from 31 October 1923 to 7 April 1924. Although annual temperatures indicate Marble Bar should be within the tropics, with a July (winter) mean of , it does not have the high precipitation requirements for hot-weather climates to sustain tropical vegetation. During December and January, temperatures in excess of are common, and the average maximum temperature exceeds normal human body temperature for six months each year. Marble Bar receives 159.6 clear days annually. Dewpoint in the summers is between . In contrast to most of the year, winters are warm, with days averaging , low humidity and clear skies. Nights from June to August can be chilly, occasionally as low as but frost is unknown. Even in mid winter however, brief bursts of heat can result in the temperature rising as high as for a few days before dropping back to normal. Rainfall is sparse and erratic, though variability is significantly less extreme than over the coastal Pilbara – the tenth percentile being vis-à-vis only in Onslow. It falls largely between December and March, with occasional rain events from autumn northwest cloudbands up to June. As little as can fall in a year; however, during heavy wet seasons when the monsoon reaches well south into the Pilbara, the rainfall can be significantly more – as much as fell between April 1999 and March 2000, and fell in 1980 owing to several tropical cyclones. The most rain recorded in a month is in March 2007, and the most in one day on 2 March 1941. North Pole A locality nearby is known as North Pole (21° 05' S. 119° 22' E.). The location's rock formations contain stromatolites in particular rock sequences, which some scientists have considered evidence that puts the origin of life on earth back to 3,400–3,500 million years ago. This has been a subject of long scientific debate. The biologic explanantion has been disputed with the argument that stromatolites older than 3,200 mya are not the result of living organisms (the definition of stromatolites includes both living and abiotic causes), the small conical structures in the Strelley Pool formation (Warrawoona Group) being formed by evaporation and a dome structure from the North Pole chert (also Warrawoona Group) being formed by soft-sediment deformation. Research by Abigail Allwood on the geology of North Pole appears to confirm the