543 



The monthly average temperatures in degrees F. at 

 9 a.m. and 4 p.m. are given below, no maximum and minimum 

 readings being available: — 



Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec. 



9 a.m. 70 65 74 oo 52 45 48 49 57 58 65 75 

 4 p.m. 105 104 99 90 89 75 65 89 90 95 103 106 



The highest shade temperature recorded is 125° F., which 

 occurred in Janua^rv. 



The rainfall is not only low but erratic. Though, 

 broadly speaking, the summer is the dry season and the winter 

 the wet one, the falls at best are too low to make the winter 

 always a season of active vegetation, whilst a heavy downpour 

 in the summer may have a marked effect in producing con- 

 siderable activity on the part of some of the annuals at least. 

 Owing to the very porous soil the rain sinks into the ground 

 as it falls, there being no sign of a watercourse in the district. 



Another feature in regard to the rainfall is the amount 

 that falls at any one time. Though the monthly total may 

 seem relatively high, if it be composed of a number of small 

 showers, as is often the case in arid Australia, the general 

 effect on the vegetation is slight. Cannon has drawn atten- 

 tion to what he terms effective and ineffective rainfalls in 

 arid South Australia, a fall of 0*15 in. in twenty-four hours 

 being insufficient to produce more than a surface wetting of 

 the soil. This important feature, which is recognized by Aus- 

 tralian pastoralists, must be remembered when considering 

 the monthly falls at Ooldea or any other station in this part 

 of arid Australia. 



The temperature records show the climate to be one of 

 •considerable extremes. Short periods of great heat, over 

 100° F. in the shade, may be expected during six months of 

 the year, while the average daily temperature at 4 p.m. 

 ^ov.-Feb. inclusive is 103° F, or over. The area, however, 

 is so open that heat is rajjidly lost by radiation at night, 

 even in summer, while in winter the diurnal range of tem- 

 perature on the soil between sun heat of the day and at 

 night is still more severe. Ground frosts are not uncommon 

 on clear nights during three or four months of the year. No 

 records of temperatures at the surface of the Soil have been 

 taken, but it is certain that they must reach very high figures, 

 especially during the summer. In August, at the time of 

 our visit, on a day on which there was a frost upon the 

 ground before sunrise, the sand at midday was so hot in the 

 «un that it was uncomfortable to touch it with the hand. In 

 summer the heat at the surface of the soil must be so great 

 as to seriously affect plants unless they are well insulated at 

 the ''collar" by cork or some other nonconductor. In this 



