Smithers
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Smithers clear sky chart from 2005-11-06 to 2024-11-03.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	10% 12% 4 11% 7% 6% 6% 5% 6% 7% 25%	102516
	Night	9% 14% 5% 12% 7% 6% 6% 5% 6% 7% 24%	96507
Transparency	Day	52% 10% 14% 17% 6%	102255
	Night	54% 11% 13% 16% 5%	96414
Seeing	Day	18% 13% 25% 26% 14% 4	16469
	Night	16% 9% 23% 33% 17% 2	23895

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	9% 18% 7% 21% 13% 7% 5% 4 5% 4 6%	2219
	11th to 20th	Day	8% 17% 6% 14% 8% 6% 5% 5% 6% 8% 18%	2199
	21st to end	Day	15% 24% 8% 17% 6% 5% 4 4 5% 4 8%	2442
February	1st to 10th	Day	9% 14% 8% 16% 9% 6% 6% 5% 5% 5% 17%	1510
	11th to 20th	Day	5% 16% 6% 9% 7% 7% 6% 5% 7% 6% 26%	1627
	21st to end	Day	4 14% 5% 12% 10% 7% 6% 5% 5% 6% 25%	1413
March	1st to 10th	Day	3 15% 7% 19% 11% 6% 5% 3 5% 4 21%	3124
	11th to 20th	Day	9% 14% 6% 12% 7% 6% 7% 5% 8% 8% 18%	3490
	21st to end	Day	5% 12% 4 10% 8% 6% 5% 4 7% 6% 32%	3825
April	1st to 10th	Day	8% 18% 5% 14% 8% 6% 7% 4 6% 6% 18%	2418
	11th to 20th	Day	7% 19% 5% 12% 8% 7% 6% 4 6% 6% 21%	2438
	21st to end	Day	11% 16% 4 10% 8% 8% 6% 4 6% 6% 21%	2517
May	1st to 10th	Day	10% 13% 4 9% 6% 5% 5% 4 7% 10% 26%	4676
	11th to 20th	Day	11% 13% 5% 12% 8% 6% 6% 5% 6% 8% 20%	4696
	21st to end	Day	12% 12% 4 11% 8% 7% 6% 5% 6% 7% 23%	5161
June	1st to 10th	Day	14% 11% 5% 12% 7% 7% 6% 5% 6% 6% 21%	2938
	11th to 20th	Day	12% 12% 4 10% 6% 6% 5% 5% 6% 8% 26%	3193
	21st to end	Day	13% 9% 4 11% 7% 6% 6% 5% 6% 7% 26%	3195
July	1st to 10th	Day	6% 4 2 6% 5% 6% 6% 5% 8% 7% 46%	4943
	11th to 20th	Day	6% 6% 3 7% 6% 5% 7% 5% 8% 11% 36%	4740
	21st to end	Day	7% 8% 3 9% 7% 6% 7% 6% 8% 9% 29%	5138
August	1st to 10th	Day	4 4 1 5% 4 4 5% 4 6% 9% 53%	4699
	11th to 20th	Day	8% 8% 3 8% 5% 5% 5% 4 7% 8% 40%	4130
	21st to end	Day	13% 11% 4 10% 6% 5% 5% 4 6% 7% 28%	4521
September	1st to 10th	Day	14% 10% 4 10% 8% 5% 5% 4 6% 8% 26%	2427
	11th to 20th	Day	13% 10% 5% 10% 7% 6% 5% 5% 7% 6% 26%	2116
	21st to end	Day	18% 13% 4 12% 6% 7% 7% 4 6% 7% 17%	2090
October	1st to 10th	Day	15% 14% 4 10% 8% 6% 5% 5% 6% 6% 21%	1928
	11th to 20th	Day	15% 14% 4 12% 6% 8% 8% 5% 7% 8% 14%	1772
	21st to end	Day	15% 14% 5% 11% 5% 5% 7% 4 6% 7% 22%	1795
November	1st to 10th	Day	14% 16% 5% 12% 8% 7% 6% 4 6% 5% 16%	1504
	11th to 20th	Day	10% 18% 7% 14% 10% 7% 6% 5% 5% 5% 12%	1368
	21st to end	Day	10% 17% 6% 14% 10% 8% 7% 6% 5% 6% 12%	1330
December	1st to 10th	Day	7% 13% 5% 15% 11% 9% 7% 7% 6% 6% 15%	1178
	11th to 20th	Day	10% 22% 6% 14% 9% 6% 6% 4 5% 6% 12%	1442
	21st to end	Day	9% 16% 6% 16% 10% 8% 8% 6% 6% 6% 10%	2314
January	1st to 10th	Night	10% 23% 8% 21% 9% 6% 5% 4 3 3 7%	4726
	11th to 20th	Night	8% 17% 6% 12% 7% 5% 6% 4 6% 7% 22%	4699
	21st to end	Night	16% 23% 8% 15% 8% 6% 5% 3 4 4 8%	5214
February	1st to 10th	Night	10% 18% 6% 14% 8% 6% 5% 4 5% 5% 18%	2669
	11th to 20th	Night	7% 15% 5% 12% 7% 6% 5% 4 7% 7% 24%	2440
	21st to end	Night	4 13% 5% 11% 8% 6% 6% 5% 7% 7% 28%	2041
March	1st to 10th	Night	3 12% 8% 17% 8% 7% 6% 4 6% 7% 21%	3729
	11th to 20th	Night	10% 14% 5% 12% 8% 7% 7% 5% 6% 6% 19%	3489
	21st to end	Night	5% 12% 4 9% 5% 5% 5% 5% 6% 7% 37%	3828
April	1st to 10th	Night	7% 11% 4 12% 8% 7% 7% 6% 7% 7% 25%	1760
	11th to 20th	Night	5% 16% 5% 12% 7% 6% 5% 4 7% 7% 25%	1691
	21st to end	Night	9% 16% 4 10% 7% 7% 6% 4 4 7% 25%	1662
May	1st to 10th	Night	8% 10% 4 11% 6% 5% 5% 5% 7% 9% 28%	2269
	11th to 20th	Night	11% 13% 5% 10% 6% 6% 6% 6% 7% 8% 22%	2199
	21st to end	Night	11% 10% 3 9% 7% 6% 5% 5% 8% 8% 28%	2414
June	1st to 10th	Night	11% 12% 4 8% 7% 6% 6% 6% 6% 8% 28%	1240
	11th to 20th	Night	8% 8% 4 9% 5% 5% 6% 5% 9% 10% 33%	983
	21st to end	Night	10% 7% 3 8% 6% 6% 7% 6% 7% 10% 30%	980
July	1st to 10th	Night	6% 3 1 4 4 4 5% 4 6% 8% 54%	2014
	11th to 20th	Night	6% 5% 2 6% 5% 5% 5% 5% 7% 10% 43%	2220
	21st to end	Night	6% 5% 3 7% 4 6% 6% 5% 7% 10% 41%	2414
August	1st to 10th	Night	4 2 2 3 3 3 4 4 5% 7% 63%	2229
	11th to 20th	Night	7% 7% 2 8% 4 3 5% 3 5% 7% 48%	2707
	21st to end	Night	13% 10% 4 10% 7% 6% 6% 5% 6% 6% 28%	3146
September	1st to 10th	Night	13% 8% 4 9% 6% 5% 5% 4 5% 7% 35%	1752
	11th to 20th	Night	9% 9% 3 10% 5% 6% 6% 5% 7% 6% 35%	2061
	21st to end	Night	16% 10% 4 11% 6% 6% 6% 6% 7% 7% 22%	2090
October	1st to 10th	Night	16% 11% 4 11% 5% 5% 5% 3 6% 6% 28%	2251
	11th to 20th	Night	16% 15% 4 11% 6% 6% 6% 5% 7% 6% 17%	2406
	21st to end	Night	13% 14% 5% 10% 6% 5% 6% 4 7% 8% 21%	2802
November	1st to 10th	Night	14% 15% 5% 12% 8% 8% 6% 5% 6% 6% 15%	2618
	11th to 20th	Night	9% 20% 6% 14% 8% 7% 6% 5% 6% 6% 14%	2812
	21st to end	Night	8% 19% 7% 15% 9% 9% 6% 4 6% 6% 13%	2850
December	1st to 10th	Night	7% 14% 6% 13% 11% 9% 7% 5% 8% 6% 15%	2982
	11th to 20th	Night	10% 18% 8% 16% 9% 6% 6% 4 6% 5% 12%	3750
	21st to end	Night	7% 18% 7% 18% 10% 8% 6% 5% 6% 5% 10%	5370

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	68% 18% 8% 5% 2	2219
	11th to 20th	Day	62% 7% 13% 6% 7% 5%	2220
	21st to end	Day	74% 11% 6% 6% 2 1	2442
February	1st to 10th	Day	64% 10% 7% 9% 9% 1	1510
	11th to 20th	Day	52% 12% 15% 15% 6%	1636
	21st to end	Day	56% 8% 11% 17% 6% 2	1413
March	1st to 10th	Day	63% 7% 7% 14% 8%	3124
	11th to 20th	Day	54% 11% 13% 17% 5%	3490
	21st to end	Day	48% 9% 14% 23% 5%	3825
April	1st to 10th	Day	60% 10% 11% 15% 3	2418
	11th to 20th	Day	62% 7% 11% 14% 6%	2438
	21st to end	Day	60% 8% 12% 14% 6%	2517
May	1st to 10th	Day	49% 12% 16% 15% 8%	4676
	11th to 20th	Day	57% 10% 11% 16% 5% 1	4699
	21st to end	Day	55% 9% 12% 16% 7%	5162
June	1st to 10th	Day	59% 8% 12% 14% 6%	2938
	11th to 20th	Day	53% 8% 16% 19% 4	3193
	21st to end	Day	54% 10% 16% 17% 3	3195
July	1st to 10th	Day	31% 7% 14% 28% 18% 2	4867
	11th to 20th	Day	35% 10% 28% 24% 3	4659
	21st to end	Day	42% 11% 19% 22% 5%	4976
August	1st to 10th	Day	25% 8% 17% 31% 19% 1	4681
	11th to 20th	Day	38% 9% 19% 26% 8%	4171
	21st to end	Day	51% 10% 19% 17% 3	4520
September	1st to 10th	Day	53% 12% 16% 17% 2	2427
	11th to 20th	Day	53% 9% 16% 18% 3 1	2116
	21st to end	Day	62% 10% 13% 11% 3	2090
October	1st to 10th	Day	57% 11% 15% 13% 5%	1928
	11th to 20th	Day	62% 13% 15% 7% 2	1772
	21st to end	Day	58% 10% 14% 16% 3	1795
November	1st to 10th	Day	66% 9% 11% 13% 2	1504
	11th to 20th	Day	70% 9% 9% 9% 4	1368
	21st to end	Day	65% 13% 11% 8% 3	1330
December	1st to 10th	Day	61% 14% 10% 11% 3	1178
	11th to 20th	Day	67% 11% 7% 11% 3	1444
	21st to end	Day	62% 17% 7% 9% 5%	2314
January	1st to 10th	Night	74% 13% 6% 5% 1	4726
	11th to 20th	Night	59% 7% 12% 8% 9% 5%	4740
	21st to end	Night	71% 15% 6% 5% 3	5214
February	1st to 10th	Night	63% 10% 8% 10% 9% 1	2669
	11th to 20th	Night	54% 9% 14% 16% 6%	2442
	21st to end	Night	50% 10% 12% 20% 8% 1	2041
March	1st to 10th	Night	54% 11% 9% 17% 8% 1	3729
	11th to 20th	Night	54% 15% 10% 16% 4	3490
	21st to end	Night	43% 10% 14% 27% 6%	3828
April	1st to 10th	Night	51% 11% 14% 17% 7%	1760
	11th to 20th	Night	52% 9% 13% 18% 6%	1691
	21st to end	Night	56% 8% 13% 18% 5%	1662
May	1st to 10th	Night	46% 14% 15% 21% 4	2269
	11th to 20th	Night	55% 10% 17% 14% 3	2199
	21st to end	Night	47% 11% 14% 23% 5%	2414
June	1st to 10th	Night	50% 9% 16% 20% 5%	1240
	11th to 20th	Night	42% 13% 18% 22% 5%	983
	21st to end	Night	45% 11% 21% 20% 4	980
July	1st to 10th	Night	25% 8% 16% 30% 21% 1	1981
	11th to 20th	Night	31% 10% 32% 23% 4	2178
	21st to end	Night	33% 12% 25% 23% 7%	2337
August	1st to 10th	Night	18% 7% 20% 39% 15%	2222
	11th to 20th	Night	34% 9% 20% 30% 7%	2732
	21st to end	Night	53% 10% 22% 14% 2	3146
September	1st to 10th	Night	46% 11% 21% 19% 3	1752
	11th to 20th	Night	44% 10% 19% 22% 4	2061
	21st to end	Night	57% 13% 12% 14% 4	2090
October	1st to 10th	Night	53% 9% 17% 16% 4	2251
	11th to 20th	Night	61% 12% 14% 10% 2	2406
	21st to end	Night	55% 13% 13% 15% 3	2802
November	1st to 10th	Night	64% 11% 10% 12% 2	2618
	11th to 20th	Night	65% 11% 10% 11% 2	2812
	21st to end	Night	67% 11% 8% 10% 3	2850
December	1st to 10th	Night	61% 12% 12% 11% 4	2982
	11th to 20th	Night	68% 9% 9% 10% 3	3747
	21st to end	Night	64% 16% 7% 8% 5%	5370

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	17% 11% 22% 32% 17% 2	180
	11th to 20th	Day	22% 11% 21% 26% 14% 7%	180
	21st to end	Day	15% 16% 17% 37% 12% 4	198
February	1st to 10th	Day	18% 16% 26% 25% 13% 3	360
	11th to 20th	Day	15% 13% 27% 32% 11% 2	365
	21st to end	Day	16% 14% 30% 26% 9% 6%	307
March	1st to 10th	Day	14% 19% 26% 23% 14% 5%	377
	11th to 20th	Day	14% 16% 28% 25% 14% 3	460
	21st to end	Day	21% 13% 24% 23% 14% 5%	506
April	1st to 10th	Day	21% 15% 29% 21% 12% 3	460
	11th to 20th	Day	18% 13% 24% 24% 16% 5%	452
	21st to end	Day	20% 21% 25% 20% 10% 4	460
May	1st to 10th	Day	20% 13% 28% 26% 10% 2	615
	11th to 20th	Day	18% 15% 21% 27% 14% 5%	675
	21st to end	Day	19% 15% 28% 26% 10% 3	735
June	1st to 10th	Day	21% 15% 25% 25% 13% 2	768
	11th to 20th	Day	14% 13% 29% 27% 14% 3	870
	21st to end	Day	15% 9% 25% 29% 18% 4	835
July	1st to 10th	Day	13% 12% 25% 30% 15% 6%	671
	11th to 20th	Day	13% 12% 27% 27% 17% 5%	668
	21st to end	Day	13% 9% 31% 29% 15% 4	739
August	1st to 10th	Day	10% 10% 23% 31% 16% 9%	676
	11th to 20th	Day	16% 11% 28% 24% 17% 4	545
	21st to end	Day	21% 14% 26% 21% 14% 4	539
September	1st to 10th	Day	23% 13% 24% 22% 14% 4	490
	11th to 20th	Day	18% 13% 19% 24% 18% 7%	490
	21st to end	Day	27% 13% 27% 19% 11% 2	490
October	1st to 10th	Day	26% 14% 21% 20% 16% 4	490
	11th to 20th	Day	24% 15% 26% 21% 11% 3	423
	21st to end	Day	23% 14% 23% 26% 12% 3	343
November	1st to 10th	Day	27% 14% 14% 30% 9% 6%	184
	11th to 20th	Day	23% 7% 16% 26% 23% 4	180
	21st to end	Day	24% 12% 15% 25% 18% 6%	180
December	1st to 10th	Day	13% 6% 15% 39% 21% 6%	180
	11th to 20th	Day	14% 7% 18% 37% 19% 4	180
	21st to end	Day	15% 5% 16% 39% 18% 7%	198
January	1st to 10th	Night	17% 11% 26% 34% 11% 1	850
	11th to 20th	Night	17% 12% 25% 34% 11% 2	850
	21st to end	Night	19% 13% 23% 30% 13% 2	935
February	1st to 10th	Night	16% 12% 27% 29% 14% 1	850
	11th to 20th	Night	15% 7% 24% 40% 13% 2	762
	21st to end	Night	11% 10% 24% 38% 15% 2	628
March	1st to 10th	Night	10% 13% 25% 30% 19% 2	760
	11th to 20th	Night	10% 13% 25% 35% 15% 2	760
	21st to end	Night	16% 10% 21% 28% 22% 4	836
April	1st to 10th	Night	12% 9% 23% 31% 21% 4	580
	11th to 20th	Night	13% 9% 22% 30% 23% 2	563
	21st to end	Night	16% 9% 25% 30% 19% 2	522
May	1st to 10th	Night	12% 8% 21% 40% 17% 1	380
	11th to 20th	Night	14% 6% 20% 35% 22% 2	374
	21st to end	Night	17% 7% 21% 35% 20%	411
June	1st to 10th	Night	16% 6% 17% 39% 20% 1	380
	11th to 20th	Night	11% 6% 28% 38% 17% 1	380
	21st to end	Night	12% 5% 20% 42% 19% 1	380
July	1st to 10th	Night	11% 5% 22% 39% 21% 1	370
	11th to 20th	Night	13% 4 20% 40% 21% 2	368
	21st to end	Night	6% 4 20% 49% 20% 2	416
August	1st to 10th	Night	9% 5% 14% 34% 37% 1	383
	11th to 20th	Night	11% 4 22% 35% 25% 2	564
	21st to end	Night	17% 5% 19% 37% 21% 1	627
September	1st to 10th	Night	17% 8% 19% 34% 20% 2	612
	11th to 20th	Night	13% 7% 20% 32% 24% 4	760
	21st to end	Night	21% 9% 23% 30% 14% 2	760
October	1st to 10th	Night	23% 10% 18% 30% 17% 2	760
	11th to 20th	Night	24% 10% 19% 31% 14% 2	760
	21st to end	Night	22% 9% 22% 32% 13% 1	836
November	1st to 10th	Night	23% 11% 27% 24% 13% 2	748
	11th to 20th	Night	19% 11% 26% 31% 11% 2	832
	21st to end	Night	18% 10% 28% 29% 14% 2	850
December	1st to 10th	Night	13% 9% 23% 37% 16% 3	982
	11th to 20th	Night	14% 9% 25% 36% 14% 2	1040
	21st to end	Night	15% 9% 25% 36% 13% 2	1026

Page generated at 2024-10-31 00:39:23. Version ac07

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