Variability of Temperature. 



141 



A similar investigation for the occasional low minimum tempera- 

 ture periods at Durban gives 83 typical instances, not, as it happens, 

 generally falling on the same day as those in the above comparison 

 for East London. In most of these there is either calm or light 

 wind, and in that respect they differ from the East London cases. 

 The annual averages are : — 



Table 7. — Mean Annual Minimum Temperature of the Cold Spells 

 at Durban, compared with the simultaneous Temperatures 

 at East London and Kimberley. 



Here we see that while the epochs come in the same order as in 

 Table 6, as might have been expected, the low temperature waves of 

 Durban are not so pronounced at East London and Kimberley as 

 the low temperature waves of East London are at Durban and Kim- 

 berley. And an examination of the individual instances shews the 

 reason to be that many of the exceptionally low tempera- * 

 tures felt at Durban are not accompanied by any great 

 fall of temperature inland, but, surprisingly enough, are 

 associated in some way with winds from the sea. Nineteen of the 

 81 cases of low temperature averaged in Table 7 were associated with 

 winds having a component off the sea, that is to say, blowing from 

 anywhere between S. round by E. to ENE. The following are 

 averages for the three stations for the nineteen occasions upon which 

 the wind at 9 a.m. at Durban came in from the sea * 



Table 8.— Average Minimum Temperatures of the Cold Spells 

 at Durban, with Sea Winds. 



* In eighteen out of the nineteen instances the wind was also blowing off the 

 sea at 3 p.m. on the previous day. 



