Bragg Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bragg Creek clear sky chart from 2005-11-06 to 2025-05-11.

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	7% 8% 3 8% 5% 5% 5% 4 7% 8% 39%	117300
	Night	5% 8% 3 8% 5% 5% 5% 4 6% 8% 41%	120352
Transparency	Day	39% 10% 15% 23% 12% 2	117048
	Night	37% 10% 15% 23% 13% 2	120250
Seeing	Day	13% 14% 30% 28% 12% 3	15880
	Night	10% 11% 34% 31% 12% 2	25124

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	1 5% 4 12% 6% 7% 7% 4 8% 8% 37%	3179
	11th to 20th	Day	1 5% 3 11% 7% 8% 6% 5% 7% 7% 39%	3315
	21st to end	Day	1 6% 2 7% 5% 5% 5% 4 6% 11% 50%	4004
February	1st to 10th	Day	1 8% 4 10% 8% 7% 7% 6% 7% 8% 35%	1600
	11th to 20th	Day	1 8% 4 10% 8% 7% 7% 6% 7% 9% 33%	1721
	21st to end	Day	1 9% 5% 13% 6% 6% 6% 5% 6% 7% 35%	1635
March	1st to 10th	Day	1 7% 4 9% 5% 5% 6% 4 6% 9% 42%	4518
	11th to 20th	Day	2 8% 4 11% 5% 4 4 4 6% 7% 42%	4902
	21st to end	Day	4 19% 8% 15% 5% 5% 5% 4 5% 7% 23%	5631
April	1st to 10th	Day	7% 16% 4 9% 7% 6% 4 4 6% 8% 29%	2431
	11th to 20th	Day	9% 15% 6% 9% 5% 5% 4 3 7% 7% 30%	2570
	21st to end	Day	11% 15% 4 8% 5% 5% 4 5% 6% 7% 32%	2600
May	1st to 10th	Day	16% 17% 4 8% 5% 5% 4 3 5% 6% 29%	4452
	11th to 20th	Day	10% 11% 3 9% 6% 5% 5% 5% 7% 8% 29%	4697
	21st to end	Day	18% 10% 3 9% 6% 6% 5% 4 5% 6% 25%	5161
June	1st to 10th	Day	18% 9% 3 8% 6% 5% 5% 5% 6% 7% 28%	2850
	11th to 20th	Day	21% 9% 4 8% 5% 5% 6% 4 6% 7% 25%	2850
	21st to end	Day	10% 5% 2 6% 5% 6% 6% 5% 8% 9% 38%	2850
July	1st to 10th	Day	7% 5% 2 6% 4 5% 5% 5% 7% 8% 47%	4740
	11th to 20th	Day	6% 4 1 4 4 4 5% 5% 9% 10% 49%	4740
	21st to end	Day	4 3 2 4 3 4 5% 4 7% 9% 55%	4956
August	1st to 10th	Day	10% 6% 2 6% 4 4 6% 5% 7% 9% 41%	4401
	11th to 20th	Day	9% 4 2 6% 5% 5% 6% 5% 7% 10% 41%	4098
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 6% 7% 51%	4521
September	1st to 10th	Day	10% 6% 2 6% 4 4 4 3 5% 7% 49%	2340
	11th to 20th	Day	13% 7% 2 6% 4 4 4 4 4 6% 46%	2095
	21st to end	Day	8% 8% 2 6% 4 4 4 4 6% 9% 46%	2090
October	1st to 10th	Day	6% 6% 2 5% 4 5% 5% 4 6% 9% 47%	3378
	11th to 20th	Day	4 7% 2 7% 4 4 5% 4 8% 11% 42%	2875
	21st to end	Day	5% 8% 2 6% 5% 5% 5% 3 5% 7% 48%	3101
November	1st to 10th	Day	5% 13% 4 9% 6% 4 6% 4 7% 6% 36%	1669
	11th to 20th	Day	3 9% 4 7% 6% 5% 4 5% 6% 7% 44%	1500
	21st to end	Day	2 10% 5% 10% 6% 4 4 4 7% 7% 41%	1400
December	1st to 10th	Day	1 6% 3 9% 6% 6% 6% 5% 9% 10% 37%	2290
	11th to 20th	Day	2 5% 4 11% 6% 7% 6% 5% 7% 11% 37%	2642
	21st to end	Day	2 10% 4 10% 6% 5% 5% 4 5% 7% 44%	3498
January	1st to 10th	Night	2 10% 6% 12% 7% 8% 7% 5% 7% 8% 30%	6766
	11th to 20th	Night	1 5% 4 12% 7% 6% 7% 5% 7% 9% 37%	6626
	21st to end	Night	1 7% 4 9% 6% 5% 5% 4 6% 8% 44%	6952
February	1st to 10th	Night	2 8% 3 9% 7% 6% 7% 5% 7% 9% 35%	2800
	11th to 20th	Night	2 10% 5% 10% 7% 6% 5% 4 6% 9% 36%	2565
	21st to end	Night	1 8% 4 11% 8% 6% 5% 4 5% 7% 39%	1993
March	1st to 10th	Night	1 7% 3 10% 7% 6% 6% 5% 7% 9% 38%	5376
	11th to 20th	Night	2 8% 3 9% 5% 5% 6% 5% 7% 9% 41%	5097
	21st to end	Night	6% 17% 6% 12% 5% 5% 4 4 6% 7% 27%	5341
April	1st to 10th	Night	5% 15% 5% 9% 6% 3 5% 4 7% 7% 35%	1968
	11th to 20th	Night	8% 14% 5% 10% 5% 4 4 3 6% 7% 35%	1781
	21st to end	Night	7% 14% 3 8% 5% 4 5% 4 6% 8% 37%	1800
May	1st to 10th	Night	16% 17% 3 7% 4 4 4 3 5% 6% 32%	2715
	11th to 20th	Night	10% 9% 3 7% 6% 4 5% 4 6% 10% 36%	2202
	21st to end	Night	14% 10% 3 7% 5% 5% 6% 4 6% 8% 32%	2414
June	1st to 10th	Night	15% 8% 2 5% 4 4 5% 5% 6% 8% 35%	1330
	11th to 20th	Night	20% 9% 2 6% 4 5% 4 4 6% 8% 33%	1330
	21st to end	Night	8% 4 2 5% 4 5% 5% 5% 7% 10% 47%	1330
July	1st to 10th	Night	6% 5% 2 5% 4 5% 5% 4 6% 7% 51%	2220
	11th to 20th	Night	5% 4 2 4 3 3 4 4 8% 9% 55%	2220
	21st to end	Night	5% 4 1 4 2 2 4 3 5% 7% 62%	2593
August	1st to 10th	Night	11% 6% 2 5% 3 3 4 4 7% 9% 46%	2529
	11th to 20th	Night	7% 3 1 5% 4 5% 5% 4 8% 10% 47%	2737
	21st to end	Night	8% 4 2 4 3 3 4 3 6% 8% 55%	3146
September	1st to 10th	Night	10% 7% 2 4 3 4 3 3 6% 7% 51%	1838
	11th to 20th	Night	13% 8% 1 4 3 3 4 3 5% 6% 49%	2085
	21st to end	Night	9% 7% 2 5% 4 3 3 3 6% 8% 50%	2090
October	1st to 10th	Night	6% 6% 2 5% 4 4 4 4 5% 7% 52%	3597
	11th to 20th	Night	4 6% 2 5% 3 4 3 4 7% 9% 52%	4050
	21st to end	Night	4 8% 3 7% 4 4 5% 4 6% 7% 48%	4457
November	1st to 10th	Night	3 13% 4 8% 5% 4 5% 4 7% 7% 39%	2610
	11th to 20th	Night	3 8% 3 8% 5% 5% 5% 5% 6% 8% 44%	2896
	21st to end	Night	2 9% 4 9% 6% 5% 5% 5% 6% 9% 41%	3000
December	1st to 10th	Night	2 7% 3 8% 6% 5% 5% 5% 8% 12% 40%	4890
	11th to 20th	Night	1 8% 4 12% 7% 6% 6% 5% 7% 9% 34%	5550
	21st to end	Night	3 10% 4 10% 5% 5% 5% 5% 6% 7% 41%	7458

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	40% 9% 12% 23% 13% 4	3179
	11th to 20th	Day	39% 9% 13% 19% 18% 3	3336
	21st to end	Day	27% 9% 15% 32% 16% 2	4004
February	1st to 10th	Day	42% 13% 13% 18% 11% 4	1600
	11th to 20th	Day	43% 10% 16% 20% 9% 2	1730
	21st to end	Day	45% 9% 15% 16% 14% 1	1635
March	1st to 10th	Day	34% 11% 14% 23% 18% 1	4518
	11th to 20th	Day	36% 8% 16% 25% 15% 1	4903
	21st to end	Day	55% 11% 13% 14% 6% 1	5631
April	1st to 10th	Day	49% 10% 16% 16% 9% 1	2431
	11th to 20th	Day	51% 8% 14% 17% 9% 1	2570
	21st to end	Day	49% 9% 15% 19% 7% 1	2600
May	1st to 10th	Day	55% 7% 11% 21% 6%	4452
	11th to 20th	Day	43% 13% 14% 21% 9%	4701
	21st to end	Day	52% 11% 16% 12% 8% 1	5162
June	1st to 10th	Day	51% 10% 15% 13% 9% 1	2850
	11th to 20th	Day	56% 8% 14% 13% 7% 2	2850
	21st to end	Day	37% 11% 18% 21% 10% 2	2850
July	1st to 10th	Day	30% 9% 14% 25% 16% 5%	4666
	11th to 20th	Day	25% 10% 19% 29% 13% 3	4659
	21st to end	Day	21% 8% 12% 26% 24% 8%	4799
August	1st to 10th	Day	35% 10% 15% 32% 7% 1	4384
	11th to 20th	Day	34% 11% 22% 25% 7% 1	4138
	21st to end	Day	28% 9% 18% 31% 12% 1	4520
September	1st to 10th	Day	34% 8% 15% 24% 15% 4	2340
	11th to 20th	Day	38% 8% 15% 24% 13% 2	2095
	21st to end	Day	35% 9% 16% 25% 13% 3	2090
October	1st to 10th	Day	31% 8% 19% 32% 9% 1	3378
	11th to 20th	Day	31% 10% 21% 22% 12% 3	2875
	21st to end	Day	34% 7% 12% 30% 15% 2	3101
November	1st to 10th	Day	44% 10% 13% 19% 12% 1	1669
	11th to 20th	Day	35% 10% 17% 25% 11% 2	1500
	21st to end	Day	39% 9% 17% 22% 9% 3	1400
December	1st to 10th	Day	36% 11% 17% 24% 10% 2	2290
	11th to 20th	Day	36% 12% 21% 22% 9% 1	2644
	21st to end	Day	37% 7% 10% 24% 18% 4	3498
January	1st to 10th	Night	46% 11% 12% 21% 7% 2	6766
	11th to 20th	Night	39% 9% 12% 19% 15% 5%	6667
	21st to end	Night	33% 11% 14% 25% 16% 1	6952
February	1st to 10th	Night	41% 12% 12% 19% 13% 3	2800
	11th to 20th	Night	43% 8% 15% 18% 13% 2	2566
	21st to end	Night	43% 7% 11% 21% 14% 3	1993
March	1st to 10th	Night	36% 11% 15% 22% 14% 3	5376
	11th to 20th	Night	34% 10% 16% 23% 17% 1	5097
	21st to end	Night	50% 12% 13% 15% 9% 1	5341
April	1st to 10th	Night	45% 9% 14% 21% 11% 1	1968
	11th to 20th	Night	48% 8% 12% 22% 9% 1	1781
	21st to end	Night	43% 9% 16% 22% 8% 2	1800
May	1st to 10th	Night	52% 7% 11% 22% 7%	2715
	11th to 20th	Night	39% 10% 15% 28% 8% 1	2202
	21st to end	Night	44% 13% 16% 18% 9% 1	2414
June	1st to 10th	Night	44% 8% 16% 22% 8% 1	1330
	11th to 20th	Night	47% 8% 16% 18% 9% 2	1330
	21st to end	Night	31% 10% 20% 26% 11% 2	1330
July	1st to 10th	Night	28% 10% 15% 23% 18% 5%	2185
	11th to 20th	Night	22% 8% 23% 33% 10% 4	2178
	21st to end	Night	21% 6% 10% 32% 24% 7%	2511
August	1st to 10th	Night	32% 9% 15% 29% 13% 1	2521
	11th to 20th	Night	28% 11% 25% 27% 9% 1	2763
	21st to end	Night	25% 7% 21% 33% 13% 2	3146
September	1st to 10th	Night	31% 7% 16% 27% 16% 4	1838
	11th to 20th	Night	34% 7% 16% 26% 13% 4	2085
	21st to end	Night	31% 8% 17% 27% 14% 3	2090
October	1st to 10th	Night	29% 8% 15% 26% 21% 2	3597
	11th to 20th	Night	26% 7% 21% 27% 17% 2	4050
	21st to end	Night	32% 8% 13% 32% 15% 1	4457
November	1st to 10th	Night	42% 8% 14% 21% 13% 2	2610
	11th to 20th	Night	36% 10% 15% 22% 16% 2	2896
	21st to end	Night	37% 9% 17% 21% 12% 4	3000
December	1st to 10th	Night	34% 11% 21% 23% 9% 3	4890
	11th to 20th	Night	40% 13% 19% 17% 10% 1	5547
	21st to end	Night	38% 9% 11% 22% 16% 4	7458

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	4 11% 33% 32% 14% 7%	200
	11th to 20th	Day	6% 11% 37% 34% 12% 2	200
	21st to end	Day	7% 16% 34% 30% 10% 3	220
February	1st to 10th	Day	9% 18% 37% 24% 7% 5%	200
	11th to 20th	Day	5% 14% 36% 36% 8% 1	284
	21st to end	Day	5% 22% 31% 32% 9% 1	399
March	1st to 10th	Day	8% 20% 38% 23% 10% 2	500
	11th to 20th	Day	7% 19% 37% 27% 8% 2	500
	21st to end	Day	12% 24% 32% 20% 9% 2	550
April	1st to 10th	Day	13% 21% 36% 24% 6% 1	500
	11th to 20th	Day	17% 18% 30% 23% 9% 2	492
	21st to end	Day	18% 21% 27% 21% 10% 3	500
May	1st to 10th	Day	20% 16% 25% 26% 9% 4	511
	11th to 20th	Day	18% 13% 22% 28% 15% 4	676
	21st to end	Day	22% 9% 22% 26% 17% 3	734
June	1st to 10th	Day	18% 14% 30% 26% 10% 2	680
	11th to 20th	Day	23% 14% 27% 23% 10% 3	680
	21st to end	Day	11% 11% 27% 31% 15% 4	680
July	1st to 10th	Day	13% 6% 25% 34% 18% 4	671
	11th to 20th	Day	11% 9% 28% 31% 18% 3	668
	21st to end	Day	6% 9% 31% 35% 15% 5%	632
August	1st to 10th	Day	12% 7% 29% 34% 13% 5%	487
	11th to 20th	Day	10% 8% 29% 34% 14% 5%	477
	21st to end	Day	12% 14% 27% 30% 13% 5%	539
September	1st to 10th	Day	14% 13% 30% 26% 13% 5%	490
	11th to 20th	Day	18% 11% 26% 30% 14% 2	490
	21st to end	Day	17% 19% 30% 24% 8% 2	490
October	1st to 10th	Day	13% 14% 30% 26% 13% 3	430
	11th to 20th	Day	12% 16% 30% 28% 11% 3	300
	21st to end	Day	14% 20% 34% 22% 7% 2	330
November	1st to 10th	Day	15% 17% 36% 25% 6% 1	300
	11th to 20th	Day	12% 15% 38% 26% 8% 2	250
	21st to end	Day	8% 16% 38% 22% 10% 7%	200
December	1st to 10th	Day	5% 11% 43% 27% 11% 4	200
	11th to 20th	Day	4 16% 34% 36% 8% 3	200
	21st to end	Day	7% 10% 31% 37% 12% 3	220
January	1st to 10th	Night	8% 14% 43% 27% 7% 1	1000
	11th to 20th	Night	6% 14% 44% 28% 7% 1	952
	21st to end	Night	7% 16% 43% 26% 7% 1	880
February	1st to 10th	Night	5% 16% 36% 28% 12% 3	800
	11th to 20th	Night	7% 13% 36% 33% 11% 1	784
	21st to end	Night	6% 9% 39% 27% 16% 2	660
March	1st to 10th	Night	5% 11% 40% 31% 11% 3	800
	11th to 20th	Night	6% 12% 39% 31% 11% 2	800
	21st to end	Night	9% 12% 32% 33% 11% 3	880
April	1st to 10th	Night	11% 12% 33% 32% 10% 2	768
	11th to 20th	Night	16% 11% 35% 29% 9%	593
	21st to end	Night	13% 12% 31% 31% 13% 1	600
May	1st to 10th	Night	17% 10% 25% 32% 15% 1	479
	11th to 20th	Night	16% 6% 25% 33% 19% 1	375
	21st to end	Night	20% 5% 23% 30% 20% 1	411
June	1st to 10th	Night	18% 8% 24% 36% 12% 1	380
	11th to 20th	Night	21% 5% 30% 28% 14% 1	380
	21st to end	Night	11% 3 24% 35% 25% 2	380
July	1st to 10th	Night	12% 4 18% 41% 24% 1	370
	11th to 20th	Night	8% 4 23% 42% 20% 2	368
	21st to end	Night	6% 6% 17% 44% 25% 2	416
August	1st to 10th	Night	14% 2 13% 39% 28% 3	378
	11th to 20th	Night	10% 3 19% 41% 25% 3	514
	21st to end	Night	11% 6% 22% 41% 19% 2	627
September	1st to 10th	Night	14% 4 25% 34% 18% 5%	698
	11th to 20th	Night	18% 6% 18% 35% 19% 5%	760
	21st to end	Night	12% 9% 34% 30% 11% 4	760
October	1st to 10th	Night	13% 8% 30% 33% 13% 3	760
	11th to 20th	Night	11% 10% 34% 30% 13% 2	760
	21st to end	Night	7% 14% 38% 31% 8% 1	836
November	1st to 10th	Night	12% 11% 44% 24% 8% 1	855
	11th to 20th	Night	8% 17% 44% 25% 4 1	1000
	21st to end	Night	6% 14% 45% 25% 8% 2	1000
December	1st to 10th	Night	6% 15% 41% 27% 9% 2	1000
	11th to 20th	Night	4 14% 44% 30% 7% 1	1000
	21st to end	Night	7% 12% 40% 29% 9% 2	1100

Page generated at 2025-05-08 07:33:58. Version ac07

Copyright © 2025 Attilla Danko.