Revelstoke
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Revelstoke clear sky chart from 2005-11-06 to 2024-11-08.

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	12% 15% 5% 11% 6% 5% 5% 4 5% 6% 26%	105941
	Night	13% 18% 6% 13% 6% 5% 5% 3 5% 5% 22%	101682
Transparency	Day	57% 7% 13% 15% 6% 1	105692
	Night	63% 7% 12% 13% 5% 1	101577
Seeing	Day	19% 11% 25% 26% 14% 5%	15670
	Night	23% 7% 24% 30% 15% 1	24053

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	12% 30% 11% 24% 7% 4 3 2 2 1 3	2193
	11th to 20th	Day	11% 21% 9% 14% 5% 5% 4 2 5% 6% 18%	2516
	21st to end	Day	19% 26% 10% 19% 8% 5% 3 2 2 2 5%	2794
February	1st to 10th	Day	12% 26% 7% 15% 8% 6% 4 2 3 4 12%	1520
	11th to 20th	Day	8% 21% 7% 15% 9% 7% 5% 3 4 4 17%	1626
	21st to end	Day	7% 24% 7% 17% 8% 7% 6% 4 4 5% 12%	1570
March	1st to 10th	Day	6% 18% 10% 20% 9% 6% 5% 3 4 5% 15%	3138
	11th to 20th	Day	6% 19% 6% 11% 6% 5% 4 4 5% 6% 29%	3254
	21st to end	Day	7% 21% 6% 14% 7% 6% 6% 4 5% 5% 16%	4165
April	1st to 10th	Day	11% 22% 7% 14% 8% 6% 5% 4 5% 4 14%	2280
	11th to 20th	Day	11% 18% 5% 12% 8% 7% 5% 4 6% 6% 19%	2341
	21st to end	Day	14% 17% 5% 12% 7% 6% 5% 4 7% 6% 17%	2568
May	1st to 10th	Day	12% 13% 4 10% 5% 6% 5% 3 5% 8% 28%	4420
	11th to 20th	Day	13% 13% 4 10% 6% 6% 5% 4 7% 8% 25%	4395
	21st to end	Day	20% 18% 4 11% 6% 5% 5% 4 5% 5% 17%	5161
June	1st to 10th	Day	22% 12% 4 9% 8% 6% 5% 4 5% 5% 22%	2872
	11th to 20th	Day	24% 13% 5% 11% 7% 6% 6% 4 5% 5% 15%	3040
	21st to end	Day	15% 10% 4 10% 7% 6% 5% 4 5% 6% 28%	3040
July	1st to 10th	Day	9% 7% 2 6% 4 4 4 4 5% 6% 48%	5060
	11th to 20th	Day	5% 5% 1 4 4 5% 4 3 5% 6% 58%	4585
	21st to end	Day	7% 5% 2 6% 4 4 5% 4 8% 9% 48%	4790
August	1st to 10th	Day	5% 4 1 4 4 5% 5% 5% 7% 9% 51%	4401
	11th to 20th	Day	8% 6% 2 6% 5% 5% 6% 5% 7% 9% 41%	4330
	21st to end	Day	13% 8% 3 9% 5% 6% 5% 4 6% 7% 34%	4321
September	1st to 10th	Day	12% 9% 3 8% 5% 4 5% 3 5% 6% 38%	2280
	11th to 20th	Day	17% 8% 4 8% 6% 4 5% 4 5% 6% 32%	2216
	21st to end	Day	18% 12% 3 11% 7% 5% 5% 4 6% 5% 23%	2090
October	1st to 10th	Day	15% 12% 4 10% 6% 7% 6% 4 6% 6% 25%	3247
	11th to 20th	Day	21% 14% 4 9% 5% 5% 6% 3 4 5% 23%	2948
	21st to end	Day	15% 20% 7% 13% 8% 7% 5% 4 5% 5% 12%	3101
November	1st to 10th	Day	22% 24% 7% 15% 7% 5% 4 2 3 3 8%	1670
	11th to 20th	Day	18% 24% 8% 14% 7% 6% 4 3 3 3 12%	1421
	21st to end	Day	14% 26% 8% 18% 9% 5% 5% 2 3 3 8%	1330
December	1st to 10th	Day	14% 23% 7% 16% 8% 8% 4 3 3 2 12%	1330
	11th to 20th	Day	11% 30% 12% 20% 8% 4 4 2 2 3 4	1682
	21st to end	Day	12% 24% 7% 15% 7% 5% 5% 3 4 5% 12%	2246
January	1st to 10th	Night	13% 35% 12% 19% 6% 4 3 2 2 2 3	4759
	11th to 20th	Night	10% 18% 7% 18% 8% 6% 6% 4 5% 5% 13%	4382
	21st to end	Night	20% 35% 10% 15% 6% 3 3 1 1 2 3	4862
February	1st to 10th	Night	12% 26% 8% 22% 8% 5% 4 3 3 3 7%	2660
	11th to 20th	Night	10% 22% 9% 17% 7% 6% 4 3 4 4 14%	2438
	21st to end	Night	8% 23% 7% 17% 9% 7% 5% 3 5% 5% 11%	1884
March	1st to 10th	Night	6% 18% 9% 20% 8% 5% 5% 3 4 7% 16%	3736
	11th to 20th	Night	7% 19% 4 11% 5% 4 4 3 4 7% 33%	3722
	21st to end	Night	9% 22% 6% 13% 6% 5% 5% 4 5% 6% 20%	3488
April	1st to 10th	Night	8% 19% 5% 12% 8% 7% 7% 5% 6% 5% 19%	1900
	11th to 20th	Night	11% 15% 5% 10% 6% 6% 6% 5% 7% 7% 22%	1789
	21st to end	Night	13% 15% 4 9% 5% 5% 4 4 5% 6% 29%	1610
May	1st to 10th	Night	11% 11% 4 11% 7% 5% 6% 4 7% 7% 29%	2540
	11th to 20th	Night	17% 11% 3 8% 5% 4 5% 5% 8% 8% 27%	2497
	21st to end	Night	24% 15% 3 9% 5% 4 4 4 4 6% 23%	2414
June	1st to 10th	Night	21% 9% 3 7% 5% 5% 4 4 6% 7% 29%	1304
	11th to 20th	Night	22% 11% 5% 8% 7% 5% 5% 3 6% 7% 20%	1140
	21st to end	Night	14% 7% 3 8% 5% 5% 5% 6% 7% 9% 32%	1140
July	1st to 10th	Night	7% 6% 2 6% 4 4 4 3 4 5% 54%	1900
	11th to 20th	Night	6% 4 1 4 3 3 3 3 5% 7% 60%	2370
	21st to end	Night	8% 4 2 5% 4 4 5% 4 6% 7% 50%	2762
August	1st to 10th	Night	4 2 1 4 4 4 5% 4 7% 10% 55%	2529
	11th to 20th	Night	8% 5% 2 6% 3 4 5% 4 8% 9% 46%	2497
	21st to end	Night	14% 8% 3 7% 4 4 5% 3 5% 7% 40%	3335
September	1st to 10th	Night	13% 7% 3 8% 4 4 5% 4 5% 5% 43%	1900
	11th to 20th	Night	17% 10% 3 6% 4 3 4 3 5% 5% 41%	1963
	21st to end	Night	18% 8% 3 9% 6% 5% 5% 4 5% 5% 33%	2090
October	1st to 10th	Night	11% 10% 4 11% 7% 6% 8% 6% 7% 7% 23%	3731
	11th to 20th	Night	20% 13% 4 8% 5% 5% 5% 4 5% 6% 25%	3983
	21st to end	Night	17% 17% 7% 13% 8% 6% 5% 4 5% 4 14%	4457
November	1st to 10th	Night	24% 24% 7% 14% 6% 4 4 2 3 3 8%	2565
	11th to 20th	Night	15% 28% 6% 16% 7% 5% 4 3 3 3 9%	2738
	21st to end	Night	14% 26% 10% 18% 7% 5% 4 3 2 3 8%	2850
December	1st to 10th	Night	13% 22% 7% 19% 10% 7% 4 2 4 3 8%	2850
	11th to 20th	Night	12% 30% 10% 21% 9% 5% 3 2 2 2 3	3510
	21st to end	Night	12% 24% 10% 20% 7% 5% 4 2 3 3 8%	5387

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	89% 5% 2 2 1	2193
	11th to 20th	Day	67% 5% 13% 7% 5% 4	2540
	21st to end	Day	87% 5% 3 3 1	2794
February	1st to 10th	Day	79% 4 6% 7% 4	1520
	11th to 20th	Day	71% 7% 10% 7% 5%	1635
	21st to end	Day	76% 6% 9% 5% 4 1	1570
March	1st to 10th	Day	72% 4 9% 10% 4	3138
	11th to 20th	Day	55% 7% 19% 18% 1	3254
	21st to end	Day	66% 9% 12% 9% 4	4165
April	1st to 10th	Day	72% 7% 11% 8% 1	2280
	11th to 20th	Day	64% 7% 15% 11% 3	2341
	21st to end	Day	66% 8% 12% 12% 2	2568
May	1st to 10th	Day	52% 9% 16% 19% 5%	4420
	11th to 20th	Day	52% 11% 16% 18% 3	4398
	21st to end	Day	64% 11% 10% 12% 2	5162
June	1st to 10th	Day	63% 7% 10% 12% 5% 2	2872
	11th to 20th	Day	68% 8% 9% 11% 3	3040
	21st to end	Day	54% 8% 12% 18% 7% 1	3040
July	1st to 10th	Day	34% 6% 9% 23% 22% 6%	4981
	11th to 20th	Day	27% 5% 11% 29% 21% 7%	4503
	21st to end	Day	29% 6% 17% 27% 16% 4	4639
August	1st to 10th	Day	26% 6% 15% 39% 13% 1	4384
	11th to 20th	Day	36% 7% 27% 22% 8% 1	4372
	21st to end	Day	45% 8% 23% 19% 4	4320
September	1st to 10th	Day	45% 7% 15% 24% 8% 1	2280
	11th to 20th	Day	50% 7% 14% 20% 9% 1	2216
	21st to end	Day	60% 8% 14% 13% 6%	2090
October	1st to 10th	Day	54% 9% 19% 16% 3	3247
	11th to 20th	Day	60% 7% 18% 14% 1	2948
	21st to end	Day	70% 7% 14% 7% 1	3101
November	1st to 10th	Day	83% 5% 6% 5% 1	1670
	11th to 20th	Day	79% 7% 6% 5% 3	1421
	21st to end	Day	80% 8% 5% 5% 3 1	1330
December	1st to 10th	Day	78% 5% 6% 9% 2	1330
	11th to 20th	Day	88% 4 4 2 2	1684
	21st to end	Day	73% 9% 9% 7% 3	2246
January	1st to 10th	Night	88% 5% 3 2 1	4759
	11th to 20th	Night	72% 6% 7% 9% 5% 1	4420
	21st to end	Night	91% 3 2 2 1	4862
February	1st to 10th	Night	82% 5% 5% 4 4	2660
	11th to 20th	Night	74% 6% 8% 8% 4 1	2440
	21st to end	Night	75% 6% 7% 8% 4 1	1884
March	1st to 10th	Night	67% 7% 9% 12% 4	3736
	11th to 20th	Night	52% 6% 24% 16% 2	3723
	21st to end	Night	61% 10% 12% 13% 4	3488
April	1st to 10th	Night	63% 9% 14% 11% 3	1900
	11th to 20th	Night	58% 8% 14% 13% 6% 1	1789
	21st to end	Night	55% 8% 17% 16% 4	1610
May	1st to 10th	Night	50% 9% 19% 18% 3	2540
	11th to 20th	Night	47% 12% 22% 17% 3	2497
	21st to end	Night	60% 8% 12% 17% 2	2414
June	1st to 10th	Night	53% 7% 15% 20% 5% 1	1304
	11th to 20th	Night	62% 8% 14% 12% 4	1140
	21st to end	Night	47% 8% 17% 19% 7% 1	1140
July	1st to 10th	Night	31% 6% 10% 21% 29% 3	1870
	11th to 20th	Night	23% 5% 11% 36% 20% 5%	2329
	21st to end	Night	30% 6% 18% 28% 16% 3	2674
August	1st to 10th	Night	23% 6% 17% 41% 12% 1	2521
	11th to 20th	Night	31% 7% 31% 22% 8% 1	2521
	21st to end	Night	43% 7% 27% 17% 5% 1	3335
September	1st to 10th	Night	42% 7% 14% 26% 10% 1	1900
	11th to 20th	Night	45% 5% 15% 22% 12% 1	1963
	21st to end	Night	52% 6% 18% 15% 8% 1	2090
October	1st to 10th	Night	52% 12% 17% 16% 4	3731
	11th to 20th	Night	56% 8% 19% 15% 2	3983
	21st to end	Night	68% 10% 11% 9% 1	4457
November	1st to 10th	Night	80% 6% 7% 5% 2	2565
	11th to 20th	Night	80% 6% 6% 5% 2	2738
	21st to end	Night	82% 7% 4 4 3	2850
December	1st to 10th	Night	80% 5% 5% 8% 2	2850
	11th to 20th	Night	89% 4 3 2 2	3507
	21st to end	Night	81% 7% 5% 5% 2	5387

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	22% 11% 26% 22% 14% 4	180
	11th to 20th	Day	19% 9% 27% 29% 13% 3	180
	21st to end	Day	17% 7% 32% 30% 11% 4	198
February	1st to 10th	Day	23% 14% 35% 21% 7% 1	180
	11th to 20th	Day	14% 16% 32% 24% 11% 4	319
	21st to end	Day	16% 13% 31% 27% 11% 2	382
March	1st to 10th	Day	16% 22% 29% 19% 10% 4	460
	11th to 20th	Day	21% 17% 24% 20% 13% 6%	460
	21st to end	Day	21% 13% 28% 22% 10% 6%	506
April	1st to 10th	Day	21% 14% 31% 24% 7% 3	460
	11th to 20th	Day	17% 15% 27% 25% 9% 6%	452
	21st to end	Day	19% 12% 27% 23% 12% 6%	460
May	1st to 10th	Day	20% 11% 24% 26% 13% 6%	463
	11th to 20th	Day	15% 11% 21% 28% 17% 9%	493
	21st to end	Day	23% 9% 16% 27% 20% 5%	734
June	1st to 10th	Day	25% 12% 27% 24% 10% 2	702
	11th to 20th	Day	26% 9% 27% 25% 11% 2	870
	21st to end	Day	17% 10% 23% 31% 16% 3	870
July	1st to 10th	Day	18% 9% 20% 32% 17% 4	856
	11th to 20th	Day	13% 8% 26% 28% 20% 6%	577
	21st to end	Day	7% 8% 24% 31% 22% 8%	531
August	1st to 10th	Day	11% 7% 24% 31% 17% 10%	487
	11th to 20th	Day	10% 9% 23% 31% 17% 9%	477
	21st to end	Day	15% 10% 23% 27% 15% 9%	539
September	1st to 10th	Day	17% 11% 23% 26% 16% 7%	490
	11th to 20th	Day	23% 10% 22% 24% 16% 5%	490
	21st to end	Day	22% 12% 26% 24% 13% 3	490
October	1st to 10th	Day	24% 8% 24% 23% 15% 6%	490
	11th to 20th	Day	28% 10% 20% 20% 14% 7%	367
	21st to end	Day	31% 8% 28% 23% 9% 2	330
November	1st to 10th	Day	30% 8% 27% 20% 12% 3	259
	11th to 20th	Day	30% 9% 23% 22% 11% 6%	180
	21st to end	Day	24% 8% 28% 19% 14% 7%	180
December	1st to 10th	Day	17% 11% 23% 22% 18% 8%	180
	11th to 20th	Day	24% 6% 28% 27% 11% 4	180
	21st to end	Day	18% 3 29% 35% 14% 3	198
January	1st to 10th	Night	32% 11% 24% 23% 8% 1	938
	11th to 20th	Night	25% 7% 30% 28% 9% 1	760
	21st to end	Night	28% 9% 27% 27% 9% 1	836
February	1st to 10th	Night	24% 9% 31% 26% 10%	760
	11th to 20th	Night	20% 6% 28% 32% 13% 1	744
	21st to end	Night	18% 8% 28% 28% 17% 1	628
March	1st to 10th	Night	22% 8% 28% 29% 12%	760
	11th to 20th	Night	21% 9% 27% 26% 16% 1	760
	21st to end	Night	21% 8% 24% 29% 14% 4	836
April	1st to 10th	Night	17% 6% 23% 37% 16% 1	760
	11th to 20th	Night	19% 6% 25% 37% 13% 1	661
	21st to end	Night	20% 6% 26% 35% 13% 1	470
May	1st to 10th	Night	16% 6% 21% 34% 22% 1	380
	11th to 20th	Night	16% 5% 24% 37% 18% 1	374
	21st to end	Night	20% 5% 18% 37% 20%	411
June	1st to 10th	Night	23% 6% 24% 38% 9%	380
	11th to 20th	Night	24% 7% 21% 32% 15% 1	380
	21st to end	Night	14% 5% 21% 36% 23% 1	380
July	1st to 10th	Night	14% 4 16% 39% 26% 1	370
	11th to 20th	Night	14% 4 18% 38% 25% 1	368
	21st to end	Night	10% 1 12% 44% 32% 1	416
August	1st to 10th	Night	7% 2 11% 37% 40% 3	378
	11th to 20th	Night	8% 3 13% 39% 34% 3	376
	21st to end	Night	13% 3 15% 40% 27% 1	738
September	1st to 10th	Night	17% 4 17% 32% 28% 2	760
	11th to 20th	Night	21% 5% 13% 32% 27% 3	760
	21st to end	Night	24% 4 21% 35% 16% 1	760
October	1st to 10th	Night	24% 4 18% 34% 18% 1	760
	11th to 20th	Night	28% 5% 21% 32% 12% 2	760
	21st to end	Night	31% 6% 23% 28% 10% 2	836
November	1st to 10th	Night	37% 7% 24% 24% 8% 1	770
	11th to 20th	Night	32% 11% 29% 19% 10% 1	838
	21st to end	Night	28% 9% 30% 23% 9% 2	950
December	1st to 10th	Night	24% 7% 30% 26% 12% 1	950
	11th to 20th	Night	27% 8% 32% 25% 7% 1	950
	21st to end	Night	25% 11% 29% 28% 7% 1	1095

Page generated at 2024-11-05 05:15:50. Version ac07

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