FEBRUARY, 191 1. MONTHLY WEATHER .REVIEFV.
THE NORMAL TEMPERATURE OF PORT0 RTCO, WEST TNDTES.
By (JLIVER L. PASSIG, Sei:tioii Director.
Porto Rico, iu coninion with most of the islnncls of the
Tropics lying within the limits of the trnclr winds, hns :I
~vttrni, but equable ani1 conifortuLle cliniatc.. The siiiall gengraphical esteiit of tlie islnncl, the niotlernte elevatilm
iibove sea level, ancl a constaiit wind. give to it a miforin
teiiiperitture cliiiracteristic of marine cliniates. Tlie
islnncl is about 100 i d e s long froin enst, to west, with an average wiilth of 40 miles, whilc the mean elevntion is
perliaps 600 feet. to ~0 0 feet h w e sea level. There is a
nttrrow belt of I~nvlaiiil aloiig tlw enst and west coasts,
n11c1 a hrosclei* belt :tloiiz the north :mil the south VoitSth.
The hills and niouiitltiiis of the interior rise al)ruptl\-
from the coastal plain to devations \-;trying froin :I few
Iiundretl to 3,500 feet. Of the 43 stations nmied in tlir scconipnnying table of avertlge temperatures 20 nrr on
the low coastal plain. The reniaining stations liave iiii
iwertige elevatinn of nbou t 1,000 feet, of wliicli 12 range
in elevation hetween 1,000 feet and 2,500 feet.
sliine is sy iiiucli mure marked tlim in liiglier latitudes. Disregard of this fact is apt to give rise to conflicting
opinions regnrtling t.einper:iture (vuiilit.ioiis baaed upim
pwsi m;d iniprwsions.
MEAN MONTHLY AND ANNUAL TEMPERATURES. .
The simplest, expression for the tempemture of a reg;( ni
is its n i ~m ~iinual temperature for a series of years.
Tlle United States Weather Bureau generally derives this d u e from reitclings of the highest ltiicl lowest teni-
penittires for eT-ery dav of the gear. The niran annunl teniperitture or tlie ishid of Porto Rico tis :I ii-liole is
7G.:3', a conifort shle and liealtliful teniper:iture ~vlien
ncconipanietl, ns it usually is in Portn Rico, by thc fresh
wincls of the northenst trades, and a relatively high per-
centage of overcast skies. Tlie stations on the coastal plnin have :I soniewlint higher nieiiii temperature, about
I
FIG. l.-Mcnn amunl temperature, Porto Biw.
C'aref ully made daily temperature obsen-ations extend-
iiig over n period of five gems in tlie Tr+cs, where c1i:tnges are siiiztll, will yield MI nvernge :innual value
wliicli is within a fraction of a clegree of the true 1iornia1 value. In Eorto Rice) tlie record of olwenxtions made
under tlie nuspices of the Vnitecl States JVeiitlier Bureau began toward tlie close nf tlie year ISW, nail therefore
covers a period of over 11 years. Tlie average length of
record per station is about S ycars; only a few of tlic
stations enumerated 111 tlie ncconipiinying t able liwe ;I
record of less than five years. while ninn~7 of them have
been in continuous operation since 1S99.
In considering temperatures of tlir :it iiiospliere it is essential to bear in iiiiiitl tlitlt, obsei-c-ntions are nlwtiys
m d e in the shade; tlint is, tlie instrunients are not esposed to tlie direct rays of the sun. This is a matter of
s ecial importance in discussing observations ninile in
t B le Tropics, where the contrnnt h?twern slix~le nnd ~1111-
;So dimg tlie nortli, west, ant1 south coasts, niicl about
i $I ' along the east const. At inland sttitions the nienn
tenipernture is below 76', varying frnni 7(io to 73',
iiccor(li1ig to eleviltion above sen-level niid other 11 i d
conditions. The lowest teniperatures we found, ns
usunl, at the higher elevations, at stntioiis from 2,000 to
2,500 feet above sen-level on the iiiain divide, a range of
momitains crossing Porto Rico froni east to west a little
south of tlie center of the island.
The ai-eruge :~iiii~i;d tenipernture of tlie islimtl lias varied but little froin the normal during tlie past I:!
gears. In 1901, the wnrniest year of the period, tlie
average T V ~S 1.3' above the nornial, and in 1907, tlie
covlest year, 0.9' below. The average temperatme wns
above norninl for tlie islrtnrl ns n wliole from 1900 to 1903,
inclusive, and iiorninl or below frnni 190-1 to 1910,
inclusive. During the year 1910 the teni Jerature con-
tinuctl hclow normal from January to Noveiii b er, inclusive.
300 MONTHIS WEATHER REVIEW. FEB~UARY, 19 1 1
Aibonito ...__.____._.____.___.___ Barras. _._...__._________.___.___ Cayey ____...____________________. Counio ..___..__________________._ Lares.. ..__.__.__._._________.__.
The departures froni year to year are indicated by the
following figures:
1599, 0.5' below normal. 1900, 0.9' above normal. 1901, 1.3O above normal. 1902, 0.5' above norinal. 1903, 0.1O above norinal. 1904, 0.3' below normal.
76 58
~
p.L 68 I 81 62 19 7 i 51 I Sti G7 1 ti?, 63 19
81 59 ' 85 65 85 63 22
66 E I ; I 89 66 23
83 87 62 25
1905, normal. 1906, 0.2' below normal. 1907, 0.9' below normal. 1905, 0.2' below norinal. 1909, 0.3' below nornial. 1910, 0.8' below norinel.
The average rlitfereni*e between the highest ant1 lowest
tiieiiii annutll temperature for all stations IS 2.3'; ttt cottst
stations it is 3', and at inland stations 2.S'.
AVERAGE WINTER AND SUMMER TEYPERATL-RES.
To those accustoniecl to the strong climatic conti-1x4s
of iniddle latitutles the difference between winter nnil
sunimer temperatures in Porto Rico seems smdl and
insignificant. While the figures do not show a iiinrkecl
is maintained between the iiieaii temperature of coast
stations and the higher inlnnd stntii:m throughout the
vear.
AFTERNOON AND EARLY MORNING TEMPERATURES.
While the mean daily teniperat.ure does not, vtiry grea tl from niontli to mouth, the diflerences between
the a !- ternoon and tlic enrly niorning tonipern tures, or
the daily rttnge, as it. is cnllcd. is comparzitirely lttrge.
-4t stations 1-111 the ininieclitite cimst., like Sail Juan, or on
t,lie sninller islantls, like C'ulehrn rtnrl Vieqiies, the cliurnul
rsiipe is influence(1 by wrroriiiding ocean tern Ieratures
tions, ant1 prnctic.nlly all the towns of Porto Rico are .2
or in~we niiles from the coast, the mean daily range 1s
froiii 30" to ?r j o , according ti-) locsl topography. The
iliurnal range is t i mntter of great iniporttxnce ttnil has
niucli to do with the personnl conifort esperiei?ced. While the nf termon temper:xtures atre c.oml~artitively
high, the night aiid early morning teniperatures are low
enough to insure cimifortitble nights throughout the year.
niitl is ciiiit,e smnll, f r w i 10' to 11'. At 11.11 in \ and sta-
1 ". ,
FIG. ?.-Meuu January temperature, Porto Rico.
cllange, the cont.rast is nevertheless very tlecitlctl. i1.s
registered by t.he factor of perstma1 coniCort. R.csit1rac.e
in the Trnpics seems to niitke one more sensitive to slight.
variations in teni )ernture, ant1 changes wliirli conic an11
iiient in the Tropics. Ji~~iuary is, on the wliole, the coolest niontli, with a
general average of 73', while the niontli of August is, 011
the whole, the wariest, with 1111 average of 79'. The
differences between the mean tempertxtures of J ~l y . August, September, :tiit1 October are, however, very
slight,. and are probably due to differences in the rnt,r 14 the wind movement, or to variations in the aiiiouiit of
cloudiness. During the winter months the mean daily teniper a t. ure
is 75' to 76' along the hniecliate coast, decreusing to 74'
over most of the constal plain. S t inlwicl stations the
mean temperature ranges between 73' nncl 6S0, dependiiig
upon the elevation of the station above sea-level.
During the sunimer and early fall the nienn tenipera- ture along the coast is SO' to Sl', although it fre uently
inland stations the niemi summer temperature varies
from 74' to 76'. A fairly constant difference of 6' to 8'
go unnoticed fnrt \ ier north are niatters of general corn-
rises to 82' or 53' along the east coast. At e P evateil
At htntions i&ng or near the coast the average tlnily
ninsiiiiuin temperature is ST', varying between Sao in
winter and S9' in summer; the average daily minimum
is i o o , varying between GG' in winter and i3''in summer. At inland stations the average daily ninsiinuni is Sao,
with limits of S l 0 in winter nnil STo in suninier, and the nvernge daily iiiiiiiniiiiii is 6 5 O , with limits of G1' in winter
ant1 6s" in summer.
d iwagc daily nia.ritiiuni and niininizini tenipmaturcs.
January. July. Yeur.
I Nus. 1 hlin. i Max. I hlin.
I
Mix. Min.
I
Range.
Coast elafioiis. I o l -; 0 :
o 1
0
Ailand stations. I I :I I l I
FEBBU~Y, 1911. MOKTBLY WEATHER IiXVlEW.
.m-l
Fro. 3.-Meean July temperature, Porto Rim.
Xd
FIG. &-Mean daily mavimum temperature (entire year), Port0 Rim.
35839-11-10
~
FIG. %-Mean dally minimum temperature (entire yearj, Port0 Rlw.
3m MONTHLY WEATHER REVIEW . FEBBUABY, 1911
The temperatures uoted in the preceding paragraphs
perature from day to day and from month to month during a series of years and the normal variations during the course of the day . In the middle and hi her lati-
such average values usually differ widely from the figures
representing actual temperatures esperienced upon any
upon the smalfer islands. like Porto Rico. large departures from normal conditions are exceptional and the figures representing avera e values do not diker greatly from
from day to day .
are average values an 8 express the normal march of tem-
tudes. especially in regions far removed from t a e coast. those expressing t 5l e actual temperatures experienced
particular da ; in the lower latitudes. and especially
TABLE 1.-Datu, mean monthly and annual tnnperatura. Port0 Rim. W . I .
.
Sept .
.
Nov .
..
72.3 71.3 76.6 79.5
71.1 77.8
7 4 6 72.3 77.8 75.6
73.9 74.4
73.9 77.9 75.2
7 6. 9
79.6
76.9 76.9 78.4 7 4 8
79.0 75.9 74.7
75.8 77.3 77.2
73.0 79.7 77.7 76.2
77.3 77.9
76.7
73.2
i7.3
n . 3
7 a o
7 a 9
7 s 8
7 s 4
7 a 3
7 a 9
.
knnual .
..
lune .
.
Dei? .
.
.
1 2
3 4
5 6 7 8 9 10 11 12
13 14
15 16
17 18 19 20 a1 !a 23 24 25
28 47
28
XI 30 31 32 33 34 35 36 37
38 39 40 41
4 e
.
Stations .
Eleva- tion in
1
feet .
NUU- ber of years .
Jan . Feb . YSr . May . July . Oet . Apr . Aug .
1.cms . 8 3
10
10 6 4
7 4 7 11 11
11 7 10
10 7 4
11 3
11 8 4 11 11
10 3 7 9 8 11 3 10
10
8 10
6
9
11 8
9 9 11 10
Feet . 1700
34 10
2. ai0 25 20
l o 0 0
75 250 20
1550
1:300 850 600 600 50 15 50
60 250
1. 200 105 1. 425
460 85
1lm 40
20
375 50
250 200 83
2:5n
2: aHJ
1’300
% 1. 5433 4.5
68.7 69.4 74.2 7ti . 2
67 . 0 75 . 5
78.9
68.5 73.7 71.8 76.0
70.8 69.6 70.0 73.4
71.4 72.7 71.1
77.0 73.8 72.ti 75.2 71.2
76.1 7 4 0
70 . 8 72.5
73.8 73 . 8 70.7
7B . 6
74.4 72.7 75.1
73.6 73.9 75.3 72 . 9
74.7 70.4
I3.S
70.4
16. 1
68.8
(i9 . 4
73.8 75.9 67.6 74ti
73.7
68.6
74.1 72.1
75.8 71.0 70.3 71.1 7 4 4 71.1 73.4 75.8 76.6 74 . 5 72 . ti
75.2 71.8 76.0 76.5
74.4 74.4
69.2 76.7 74.7 72.6 75.0 74.2 74.4
75.4 72.7
7 4 9 70.2
76.3 74.0
70.4
70.9 72 . a
68.6 70.0 73.9
75.9 68.8 75.2 7 4 5 71.1 69.3 74.5 72.7
7 6. 5 70 . 8
70.6 75.4
72.9 77.1 76.8 75.3 74 2 7s . 5 71.5
76.9 75.8 71 . S 72.8 74 . s 74.7
ti9 . 8 77.1 75 . 1 72.4 75.8 74.7
74.5 75.5 73.6 75.6 70.3
76.9 74.4
70.5
70.9
10.4 73.2 76.0 78 . 0
70.8 76.2 75.9 72.6 71.2 76.1 75 . 2
71.9 72.5 72.9 76.8 74.0 75.0 77.7 78.4 76.2 75 . li 76.9 73.2 78.0 76 .ti
73.4 73.8 7ti . 9 76.4
79.0 76.4 75.4 77.5 76.3 75.8 77.3
76.2 77.3
71.9 77.8
76.7
7 8 4
7 0. ti
72.7 73.2 77.8
w . 0 72.3 78.2 78.2 74.5 73.5
77.9 77.6 80.1 72.5 74.9 74 . 4 77.4 77 .ti
76.9 79 .ti
80.4 77.8
75.0
7 4 9
7X 8 78.5 75.3 75.7 79.1 78.4
79.Y 80.2 78.1 77.0 79.1 77.7
77.6
78.0
73.9 79.7
79.3
7 a 2
7a 4
7 a 8
78.8 74.4
79.0 80.6 75.7
79.4 77.1 76.2
78.5
80.7 75.4 78.7 76.1 w.5 78.2 78.5 81.2 81.6 79.0
79.3 Bail
77.2 80.9 79.6 77.0 77.3 79.6
74.3 8Y . Y 79.2
80.3 79 . 4
80.0 80.2
78.8 80.4 75.5 81.1 79.6
7 a 8
7s 9
80 . 2
7 a 1
7 4 5 78.9 79.0 x1.4 76.1
7Q . 7 77.4
76.3 79.3 78.8
so . 9 75.9 78.2 76.4 81.1
81 . S 82.3
79.5 79.5 s a 2 77.3
80.9
79.2 77.4 77.7
s(x6
80.7 75.1
88.0 79.5
81.2
79.5 80.1 80.6 79.4 81.0
75.7
81.3 80.1
7 a 9
7 8 3 7 a 7
7 s 7
74.2 73.7 79.” 81.3
75.0
79.7
7 6. 7 74.5 79.6 78.5
Po . 7 75.1 77.0 78.4
79.5
79.1 81.4 81.4
79.6 79.3 79.8 76.8
W.9 79.0 76.7 77.3
8 a O 80.1 74.9
81.9 79 .ti
78.1 80.7 79.1 80.2 80.7 79.0
80.5 75.4
19.9
7 8 6
7 8 5
E l . 0
73.2 78.1 78.6 s a 7 7 4 6 79.0
76.4 73.8
77.1 79.8 74.8 76.3 74 9
79.0 77 .ti
7 a ti
80.6
w.7
79.3 75.9
80.0 77.8 76.2
79.1 74.7 81.5 79.2 77.5 80.1 78.0
79.5 80.1
80.0 75 . 0
80.1
79 . I
7 a 9
7 8 9
7 a 8
7a 5
76 . a 7a 9
7 a a
70.1 70.3 75.1 77.2
68.0 75.3 7 4 5 72.6 70.4 75.2 72.7 75.7 72.4 71.8 71.0 75.9 73.2 74.3 77.1 77.2
7 4 9 74 3 76.3 72.1
77.7 73.9 71.8 73.3 75.6 7 4 7 70.9 77.0 75.8 72.8 76.5 75.2 75.7
76.4 73.7 71.7
7 6. 7 5. I
70.9
11.8 12.2 76.9 79.0 71.8 77.3 77.1 74.0
72.5 77.0 75.8 78.0
73.3 7 4 3
73.5 77.5
75.3 76.3 79.0 79.4
77.2 76.6 77.9
7 4 4
77.1 74.4 75.2 77.5 77.4 72.4 79.7 77.4 75.8
77.0 77.3
76.5 78.1 73.1
77.4
78.x
713.3
7 a 2
7 a 8
Adjuntas ................................... Alto de la Banders .......................... Aguadllla (Coloao) ..........................
Anasco ...................................... Arecibo (Town) ............................. Bacupey (near Aredbo) ..................... B- ...................................... Bayamon ................................... mguas ...................................... catlovanas .................................. Carmelita(1) ................................
Goa ...................................... comer0 .....................................
Culebm ..................................... Fajar& .................................... Quanlca ..................................... Humacao .................................... Isabela ......................................
Juana Iaz .................................. was ....................................... Lares ....................................... Las Maria8 .................................. Laquill0 (1) ................................. Manatl ...................................... MarIcao ..................................... Maunabo .................................... Mayaguer ................................... MoroviS ..................................... PonCe ....................................... Rio Bbnw ................................. San German ................................ San Juan ................................... san Lorenm ................................ Sank Isabel ................................ Utuado San Salvador) ..................... ViequeaLand .............................. Yanm ......................................
.................................... hck. ...................................
c$yl3~ ...................................... ......................................
cor02 1 .....................................
I s O l i I l ~ ....................................
Means ............................... .I ......... ....... 78.0 73.2 73.6 75.3 77.1 78.1 7 a 7 79.0 7 a 5 77.9 76.4 74.2 76.3
Nonc.-MaxIma and minima are In bold face figures.