54 
PACIFIC SCIENCE, Vol. IV, January, 1950 
The 41 -year data, reported on in 1943, 
smoothed to hundredths as 7-day progressive 
means, gave September 6, with 78.51°, as 
the warmest date. The 17-year data gave a 
run of 7 days with 78.6°, from August 16 
through August 22. From these, August 19 
may be taken as the warmest date, and agree- 
ing well with the August 20 date from the 
58-year graph. 
The 36-day long "plateau” of Figure 2 was 
subjected to further study by means of 18 
graphs of 7 -day progressive means, from 
July 15 through September 25, for the 18 
years from 1931 through 1948. On these 
graphs there were found a total of 43 dates 
which either had the maximum temperature 
for the year in question or were tied for the 
maximum. They ranged from as early as 
July 22 to as late as September 25, a range 
of 65 days. The mean and median dates were 
both August 23. The standard deviation was 
14.5 days, a large value that implies uncer- 
tainty as to the date of the mean. Inspection 
of the 18 graphs showed a great variation — 
some were relatively smooth and some rather 
"wavy”; some showed a single maximum and 
some showed several scattered dates tying for 
the maximum; and, of course, the dates of 
the maxima varied greatly as described above. 
The plateau of 36 days duration contrasts 
strongly with the wavy curve of the first 
months of the year. The difference is thought 
to be due to differences in the altitudes of 
the noon sun. In winter the altitude of the 
noon sun decreases steadily to a minimum 
about December 21 and then increases stead- 
ily. But in summer the noon sun on two 
occasions crosses the zenith of Honolulu, in 
21° 18' N. Lat. The noon sun is nearest the 
zenith about May 26 and again about July 16. 
On about June 21 the noon sun is 2° 9' north 
of the zenith, and it is the same amount south 
of the zenith about May 16 and July 26. 
Thus for the period of 71 days between these 
two dates the noon sun is very high. During 
this time, also, the length of the daylight day 
varies only 17 minutes — that is, from 13 
hours and 9 minutes to 13 hours and 26 min- 
utes. Thus there is a long period in which 
the insolation is not only strong but is very- 
uniform, which uniformity may well explain 
the plateau or long sequence of days of uni- 
formly high average temperatures. 
LAGS 
If we select February 13 as the coldesr 
date, we find that it falls 54 days after the 
winter solstice. Similarly, August 20 fails 
60 days after the summer solstice. These 
dates divide the year into somewhat unequal 
parts. It takes 188 days to warm up from 
the coldest to the warmest date, but only 177 
days to cool down again. 
The most rapid cooling is from Novem- 
ber 1 to November 26, during which time 
the 7-day progressive means drop 2.5°, from 
76.3° to 73.8°, or at a rather steady rate of 
a tenth of a degree per day. 
A longer period of fairly steady warming 
up extends from March 28 to June 15, with 
a rise of 4.8°, from 72.0° to 76.8°, in 78 
days, or at a rate of about 0.06° per day. This 
period of rising temperature is not as steady 
or as rapid as the drop in November, but a 
short period of 10 days, from May 10 to 
May 20, gives a steady rise of about a tenth 
of a degree per day. 
CONCLUSIONS 
We have been considering only one ele- 
ment of the weather, namely the physical 
temperature, but the impression that the hu- 
man animal gets of temperature is strongly 
modified by the effects of air movement and 
of humidity. 
It appears that, on the average, the coldest 
date is February 13 and the warmest date is 
August 20. But, despite the alleged monot- 
onous uniformity of Hawaiian weather, the 
dates of warmest and coldest temperature in 
any one year may come as much as a month 
earlier or later than the average dates. It also 
appears that the cold season may include sev- 
eral irregular fluctuations of temperature. 
