teem!

On the coast, in the latitude of Prince Rupert and
thereabouts, the last frost May occur early in March or as
late as the last week of May but generally from April 15 to
May 1. At higher levels along the coast, as at Stewart,
there may be a June frost. No doubt, if there were many
reporting stations, the pattern of frost-incidence near the
coast-line would be found to be very complex, depending
upon such factors as elevation, low-lying pockets with
glaciers nearby, mountains that cut off the rays of the rising
sun and so allow the nocturnal fall of temperature to
continue an hour longer in the shadow area. An intelligent
homesteader might be able to realize the significance of
these disadvantages before taking up land, or a federal
advisory commission might survey the lands before offering
them for settlement, taking such factors into account.
Aside from these factors, however, there is a very large

- variation from year to year on the coast. At Prince Rupert,
where nearly all other causes except airmass movements
may be ignored, the mean square variation from the average
of the length of the frost-free period is 22-78 days. Since
the average is 195 days, it may be said that the coefficient

Dates in Year-Days

eit Ca cn Gotti eas Jan. 1....Year-Day 1

of variability is 12 per cent. The extreme positive deviation
on record is 56 days in 1915 and the extreme negative
42 days in 1924. At New Hazelton the standard deviation
is 23 days or 39 per cent; at Terrace, 24 days or nearly
19 per cent; at Prince George, 24 days or 37 per cent; at
Barkerville, since 1888, 271 days or a little more than
50 per cent. Babine Lake also has a similar standard devia-
tion, 234 days or nearly 40 per cent. Farther south on the
Chilcotin River, near Hanceville, B.C., 38 yeats’ record
gives a deviation of 274 days or 53 per cent. Here,
also, is an opportunity to check with the ranch-owners at
Redstone, Alexis Creek, Hanceville, Big Creek, and Pun-
chaw to see what can be done with an average frost-free
period of 50 to 60 days, subject to a variability of 40 to
5O per cent. There is a long record of ranching (cattle
mostly) at Barkerville, and shorter period-efforts at other
places on that plateau. From a knowledge of what has
been tried and failed at all these ranches, there might be
attached an agricultural meaning to these percentages of
variability that could be used to predict the feasibility
of culture elsewhere in the interior of British Columbia.

Rebel tes ee. Year—Day 32 Deer si ys Year—Day 365

Last Frost of Spring

First Frost of Autumn Average
Station - Frost-Free
Earliest Latest Average | Earliest Latest Average Period
Days Days Days Days Days Days Days
DENSE SR 2 S52 Sy -sac tele ne ele aaa eee eee 133 195 158 200 258 232 74
Suede, Cecelen te ait ithe Lik eh ecat css mo 144 171 152 200 253 ORS 79
CARSRSSS, 5. gece SESS ea eo ee 152 196 178 199 250 221 43
INCL 6S tg ae SG Ee Re a a a IE 148 192 164 198 264 249 85)
peor Mc Rhereoni tits ist at Se. as eon Gk SG 147 195 162 ~ 199 258 233 71
pace Nommanere saa ei ee aS 149 195 173 200 25 218 45
PGES On tg eae ee eee ee a ee 131 195 156 203 269 240 84 —
Ores Good EH ope jen cauticte ty Ape. bases Shion oa ee 145 196 166 199 245 218 52
HOHE IR) IBS acer ren acc ae te Ue ie nS a 140 195 162 216 268 255 93
Be VEE eta st ar tie ie Oe 137 182 162 213 272 249 87
PEC eo see stat ees PRI Oa Py Pe th 137 173 155 | 201 251 221 66

(The average frost-free period is 70 to 72 days for both
the Yukon and the Mackenzie. The very short periods
at Carcross and Norman suggest that local topography may

_ lower the general average materially at many places from

is 21 days at Fort Good Hope and 20 days at Dawson, or 26
per cent and 40 per cent. Fort Simpson has a standard
deviation of 19 days or 22 per cent, Mayo, 14 days or 27

per cent. The frost-free period has varied from 34 days in
1917 to 114 days in 1942 at Dawson, and at Fort Simpson
from 42 days in 1900 to 120 days in 1938.

_ which no record is available. Note that the last spring
\ frost or the first autumn frost may occur in July. The
| standard deviation from the average of the frost-free period

\

Dates in Year—Days............... Grok, = -Year—Day 1 ED leer Year—Day 32 Decne .Year—Day 365

Last Frost of Spring

First Frost of Autumn Average
Station : Frost-Free
Earliest Latest Average | Earliest Latest Average Period
Days Days Days Days Days Days Days
INGLES ‘SEs, [OIEC SS eye tes a a eee 119 179 142 208 273 251 109
_E USI olson [pCi 6h eC Ue aa aL 143 191 166 203 256 234 68
Rone Gener n mnenit nk eae ne Se eS 154 187 166 200 254 232 66
SLAVS TSI 1s es 9 ae a RES 131 190 155 209 279 247 92
IBGE? ILLS «5c hz oreey Ua eee ea ela 144 192 162 202 248 228 66
DIESE SUE cece) cl Rae aie en an a Coen Cra 136 193 160 198 261 238 78
CHGEEACE Ce Seo gigaeac ne ea a Ee SES 131 186 160 204 255 239 79
(Cee Cle TREE bs oes a a ee 126 194 156 198 251 230 74
Hetecuplave Bakere risk sts) they ie ees ee 132 189 159 219 273 243 84
REIN GION /ci5 Gitalo yo Con CEM nS 129 164 147 237 299 258 lil
Gagatarel Giiyeatn) ae eet ee ce et es 169 190 179 202 219 209 30
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