FROST 
Owing, however, to the fact that or- 
chardists have not taken up the idea of 
orchard heating to the extent that has 
characterized certain other sections, 
there has not been given the careful 
study to conditions here as elsewhere. 
COLORADO 
Grand Junction District 
The most distinctive climatic feature 
of this section, especially of its lower 
valleys, is the comparative uniformity 
of the weather conditions from day to 
day. This is due to the high mountains, 
which practically surround the section 
and deflect the course of low pressure 
areas. <A. storm approaching from the 
west will usually cross the Continental 
Divide either to the north or the south 
of Colorado, where the height of the 
mountains is less. In consequence, the 
sudden changes that attend the passing 
of a low center are rarely experienced 
here. Severe cold waves, so common 
on the Eastern plains, are comparatively 
rare. There is, on the contrary, a ten- 
dency for a stationary area of high pres- 
sure to form over this region in winter, 
where it may remain for days, and even 
weeks, together. When one of these 
highs controls the weather, the sky is 
clear, the wind light, and of the moun- 
1019 
tain and valley type, the day tempera- 
tures are moderately high and remark- 
ably uniform, and the nights cool, but 
seldom excessively cold, except when the 
ground is covered with snow, and where 
the air drainage is poor. 
The annual mean temperatures range 
from 52.5 degrees, at Grand Junction, to 
less than 32 degrees, at the higher levels. 
The night temperatures depend large- 
ly on the topography, air drainage exert- 
ing a greater control over this factor 
than does the absolute elevation. The 
mildest weather, in cold spells, is found 
where the night wind is the strongest, 
which is usually below the larger can- 
yons. The comparative freedom from 
frost experienced by such regions has 
led to the development of an extensive 
fruit-growing industry. 
The growing season, or interval when 
frost is not to be expected, varies great- 
ly in different localities. Where longest 
(in the Grand valley), it extends from 
early in April to late in October; above 
9,000 feet, frost may be expected every 
month. It is probable that the growing 
season is longer, in most localities, than 
is indicated by the attached frost table; 
a temperature of 82 degrees, which is 
taken as the standard, is not generally 
destructive to the staple crops. 
Average Date of Killing Frosts 
Length Precipi- 
of record Last in First in tation 
Stations years Spring Fall Av. Annual 
Inches 
Cedar Edge... ... 2.0 once ee ce eee May 20 Sept. 23 11.02 
Colbran. ee beeen ee Le nee 8 May 26 Sept. 24 15.16 
Delta... ccc cece eee ce ee ees May 16 Sept. 25 7.82 
Durango...... Le eee Lae 12 May 28 Sept. 26 17.51 
Grand Junction....... 0 © 2.5.2 wees 16 April 18 Oct. 18 8.74 
Grand Valley....... 0 .........02 2 eee 14 May 10 Sept. 29 12.30 
by 9 June 16 Sept. 6 12.70 
Mancos...... 6.06. cee eee e cee eee 10 June 9 Sept. 17 16.88 
Meeker... ....... 00... cece cee eee nee 14 June 12 Sept. 12 16.10 
Montrose. ........ 000. ec cece ee eee oe 10 May 16 Oct. 2 9.50 
Pagoda...... 0. cee eee ek tee ee 13 June 12 Sept. 3 18.26 
PA@ONIa.. 6. eee cee eee 8 May 5 Oct. 3 12.16 
Silt... eee eee eee 12 May 21 Sept. 27 11.99 
T. S. Ranch............ 0.000 e eee ee eee 8 April 27 Oct. 10 10.69 
