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 2026-09-14.

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% 41%	154080
	Night	5% 8% 3 8% 5% 5% 5% 4 6% 8% 42%	145736
Transparency	Day	37% 9% 16% 24% 12% 2	153786
	Night	36% 9% 16% 24% 13% 3	145613
Seeing	Day	13% 14% 30% 28% 12% 3	17771
	Night	10% 11% 35% 31% 12% 2	26700

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 4 4 11% 6% 7% 7% 5% 8% 9% 38%	4125
	11th to 20th	Day	1 4 3 11% 6% 7% 5% 4 7% 7% 46%	4317
	21st to end	Day	1 6% 3 9% 5% 5% 4 4 6% 11% 48%	5186
February	1st to 10th	Day	1 8% 4 10% 8% 6% 6% 6% 7% 8% 35%	1680
	11th to 20th	Day	1 8% 4 9% 8% 7% 7% 5% 7% 9% 35%	1810
	21st to end	Day	1 9% 5% 13% 6% 6% 6% 5% 6% 7% 35%	1714
March	1st to 10th	Day	1 7% 4 9% 5% 5% 6% 4 6% 9% 42%	4618
	11th to 20th	Day	2 8% 4 11% 6% 4 4 4 7% 7% 42%	5010
	21st to end	Day	4 19% 8% 15% 5% 5% 5% 4 5% 7% 23%	5755
April	1st to 10th	Day	7% 16% 4 9% 7% 6% 4 4 6% 8% 29%	2553
	11th to 20th	Day	9% 15% 6% 9% 5% 5% 4 3 6% 7% 30%	2700
	21st to end	Day	10% 15% 4 8% 5% 5% 4 5% 5% 7% 31%	2730
May	1st to 10th	Day	11% 12% 3 7% 5% 5% 5% 4 6% 7% 37%	8000
	11th to 20th	Day	10% 12% 4 10% 6% 6% 7% 5% 7% 8% 26%	8755
	21st to end	Day	13% 7% 2 7% 5% 5% 5% 4 7% 8% 34%	9649
June	1st to 10th	Day	17% 8% 3 8% 5% 5% 5% 5% 7% 8% 29%	3150
	11th to 20th	Day	20% 9% 3 7% 6% 5% 6% 4 6% 7% 26%	3150
	21st to end	Day	10% 5% 2 6% 5% 6% 6% 5% 8% 9% 37%	3150
July	1st to 10th	Day	6% 4 2 5% 4 4 5% 5% 7% 9% 49%	8820
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 8% 9% 48%	8820
	21st to end	Day	7% 4 2 4 3 3 4 4 6% 8% 55%	9219
August	1st to 10th	Day	7% 5% 2 6% 4 4 5% 5% 7% 8% 47%	6441
	11th to 20th	Day	13% 5% 2 6% 5% 5% 5% 5% 7% 9% 39%	6036
	21st to end	Day	7% 4 2 5% 4 4 4 4 6% 8% 54%	6570
September	1st to 10th	Day	11% 6% 2 6% 4 3 4 4 5% 8% 47%	2586
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 4 6% 46%	2239
	21st to end	Day	8% 7% 2 6% 4 4 4 4 5% 9% 47%	2200
October	1st to 10th	Day	6% 6% 2 5% 4 4 5% 4 6% 9% 48%	3485
	11th to 20th	Day	4 7% 2 7% 4 4 5% 4 8% 11% 42%	2966
	21st to end	Day	5% 7% 2 6% 5% 5% 5% 3 5% 7% 49%	3200
November	1st to 10th	Day	5% 12% 4 9% 6% 4 6% 4 6% 6% 37%	1754
	11th to 20th	Day	3 9% 4 7% 6% 5% 4 5% 6% 7% 44%	1575
	21st to end	Day	2 10% 5% 11% 6% 4 4 4 7% 8% 40%	1470
December	1st to 10th	Day	1 6% 3 9% 6% 6% 6% 5% 9% 10% 37%	2360
	11th to 20th	Day	2 5% 4 11% 6% 7% 6% 5% 8% 11% 36%	2712
	21st to end	Day	2 9% 4 10% 5% 5% 5% 4 5% 7% 44%	3575
January	1st to 10th	Night	2 9% 5% 10% 7% 8% 7% 5% 7% 9% 33%	8768
	11th to 20th	Night	1 5% 3 11% 6% 6% 6% 5% 7% 9% 42%	8624
	21st to end	Night	1 6% 3 10% 6% 6% 6% 5% 6% 8% 42%	8994
February	1st to 10th	Night	2 8% 4 9% 7% 6% 7% 5% 7% 9% 35%	2940
	11th to 20th	Night	2 10% 5% 10% 7% 6% 5% 5% 6% 9% 35%	2696
	21st to end	Night	1 8% 4 11% 8% 6% 5% 4 6% 8% 39%	2089
March	1st to 10th	Night	1 7% 3 10% 7% 6% 6% 5% 7% 9% 38%	5496
	11th to 20th	Night	2 8% 3 9% 5% 5% 6% 5% 7% 9% 41%	5209
	21st to end	Night	6% 17% 6% 12% 5% 5% 4 4 6% 7% 27%	5459
April	1st to 10th	Night	5% 15% 5% 9% 6% 3 5% 4 7% 7% 35%	2066
	11th to 20th	Night	7% 14% 5% 10% 5% 5% 4 3 6% 7% 35%	1871
	21st to end	Night	7% 14% 3 9% 5% 4 5% 4 6% 8% 36%	1890
May	1st to 10th	Night	11% 13% 2 6% 3 3 4 3 5% 8% 42%	4914
	11th to 20th	Night	10% 11% 4 8% 5% 4 5% 4 7% 10% 31%	4105
	21st to end	Night	9% 7% 2 7% 5% 5% 5% 5% 7% 8% 39%	4522
June	1st to 10th	Night	15% 8% 3 6% 5% 4 5% 5% 6% 8% 35%	1470
	11th to 20th	Night	18% 8% 2 6% 4 5% 4 4 6% 8% 34%	1470
	21st to end	Night	9% 4 1 5% 4 5% 5% 5% 7% 9% 46%	1470
July	1st to 10th	Night	5% 5% 2 5% 3 5% 4 4 6% 8% 52%	4140
	11th to 20th	Night	7% 4 2 4 3 3 3 3 6% 8% 56%	4140
	21st to end	Night	10% 5% 1 4 2 2 4 2 5% 7% 58%	4846
August	1st to 10th	Night	10% 6% 2 6% 3 3 4 4 6% 7% 49%	3709
	11th to 20th	Night	12% 4 1 5% 4 5% 5% 5% 8% 10% 41%	4023
	21st to end	Night	6% 3 1 4 3 3 4 3 6% 9% 57%	4578
September	1st to 10th	Night	10% 7% 2 4 3 4 3 3 6% 7% 51%	2032
	11th to 20th	Night	13% 8% 1 4 3 3 4 3 5% 6% 49%	2228
	21st to end	Night	9% 7% 2 5% 4 3 3 3 7% 8% 50%	2200
October	1st to 10th	Night	6% 6% 2 5% 4 4 4 4 5% 7% 52%	3710
	11th to 20th	Night	5% 6% 2 5% 3 4 3 4 7% 8% 53%	4179
	21st to end	Night	4 8% 3 7% 4 4 5% 4 6% 7% 48%	4600
November	1st to 10th	Night	3 12% 4 8% 6% 4 5% 4 7% 7% 39%	2744
	11th to 20th	Night	2 8% 3 9% 5% 5% 5% 5% 6% 8% 43%	3041
	21st to end	Night	2 9% 4 9% 6% 4 5% 4 6% 9% 41%	3150
December	1st to 10th	Night	2 7% 3 8% 6% 5% 5% 5% 8% 12% 39%	5040
	11th to 20th	Night	1 8% 4 12% 7% 6% 6% 5% 7% 9% 34%	5700
	21st to end	Night	3 10% 4 10% 5% 5% 5% 5% 6% 7% 41%	7623

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	36% 9% 13% 23% 14% 4	4125
	11th to 20th	Day	34% 8% 14% 25% 16% 3	4338
	21st to end	Day	29% 9% 16% 30% 16% 1	5187
February	1st to 10th	Day	41% 12% 12% 18% 11% 4	1680
	11th to 20th	Day	42% 10% 15% 21% 10% 2	1819
	21st to end	Day	44% 9% 15% 16% 14% 2	1714
March	1st to 10th	Day	33% 10% 14% 23% 18% 1	4618
	11th to 20th	Day	35% 8% 16% 25% 15% 1	5011
	21st to end	Day	55% 11% 13% 14% 6% 1	5755
April	1st to 10th	Day	48% 10% 17% 16% 8% 1	2553
	11th to 20th	Day	51% 8% 15% 17% 9% 1	2700
	21st to end	Day	49% 8% 14% 20% 7% 1	2730
May	1st to 10th	Day	43% 8% 11% 24% 13% 1	8000
	11th to 20th	Day	47% 12% 12% 19% 8% 2	8759
	21st to end	Day	41% 10% 19% 21% 8% 1	9650
June	1st to 10th	Day	49% 10% 15% 15% 10% 1	3150
	11th to 20th	Day	53% 9% 14% 15% 8% 2	3150
	21st to end	Day	38% 11% 19% 21% 9% 2	3150
July	1st to 10th	Day	27% 9% 17% 27% 16% 3	8746
	11th to 20th	Day	28% 10% 17% 26% 14% 5%	8739
	21st to end	Day	25% 7% 13% 28% 20% 7%	9019
August	1st to 10th	Day	30% 9% 15% 31% 9% 4	6424
	11th to 20th	Day	37% 11% 23% 23% 6% 1	6076
	21st to end	Day	25% 8% 19% 35% 12% 1	6569
September	1st to 10th	Day	35% 8% 16% 24% 15% 4	2586
	11th to 20th	Day	37% 8% 15% 25% 14% 1	2239
	21st to end	Day	34% 9% 16% 26% 12% 3	2200
October	1st to 10th	Day	31% 8% 19% 32% 9% 1	3485
	11th to 20th	Day	31% 10% 21% 22% 13% 3	2966
	21st to end	Day	34% 7% 12% 30% 16% 2	3200
November	1st to 10th	Day	44% 10% 13% 19% 13% 2	1754
	11th to 20th	Day	35% 10% 17% 25% 11% 2	1575
	21st to end	Day	40% 9% 17% 22% 9% 3	1470
December	1st to 10th	Day	36% 11% 17% 24% 10% 3	2360
	11th to 20th	Day	36% 12% 20% 21% 9% 1	2714
	21st to end	Day	37% 7% 10% 24% 18% 4	3575
January	1st to 10th	Night	42% 10% 12% 21% 11% 2	8769
	11th to 20th	Night	35% 8% 15% 21% 14% 6%	8665
	21st to end	Night	35% 10% 16% 24% 14% 1	8994
February	1st to 10th	Night	40% 12% 12% 19% 13% 3	2940
	11th to 20th	Night	43% 8% 15% 18% 13% 2	2697
	21st to end	Night	42% 8% 11% 22% 14% 3	2089
March	1st to 10th	Night	36% 11% 15% 22% 14% 3	5496
	11th to 20th	Night	34% 10% 16% 23% 17% 1	5209
	21st to end	Night	50% 12% 13% 15% 9% 1	5459
April	1st to 10th	Night	45% 9% 14% 21% 11% 1	2066
	11th to 20th	Night	47% 8% 12% 22% 9% 1	1871
	21st to end	Night	45% 9% 15% 22% 8% 2	1890
May	1st to 10th	Night	40% 6% 12% 25% 17% 1	4911
	11th to 20th	Night	44% 9% 13% 26% 8%	4105
	21st to end	Night	37% 10% 18% 27% 8% 1	4526
June	1st to 10th	Night	44% 8% 15% 23% 9% 1	1470
	11th to 20th	Night	45% 8% 16% 19% 9% 2	1470
	21st to end	Night	32% 10% 20% 27% 10% 1	1470
July	1st to 10th	Night	26% 9% 18% 29% 15% 3	4105
	11th to 20th	Night	25% 7% 19% 30% 12% 6%	4098
	21st to end	Night	25% 6% 16% 28% 20% 6%	4741
August	1st to 10th	Night	31% 8% 15% 28% 13% 5%	3701
	11th to 20th	Night	34% 11% 26% 23% 6% 1	4049
	21st to end	Night	21% 7% 23% 35% 13% 1	4578
September	1st to 10th	Night	31% 7% 17% 27% 15% 3	2032
	11th to 20th	Night	33% 7% 16% 27% 13% 4	2228
	21st to end	Night	30% 8% 17% 28% 14% 3	2200
October	1st to 10th	Night	29% 8% 15% 26% 20% 2	3710
	11th to 20th	Night	26% 7% 20% 26% 18% 2	4179
	21st to end	Night	32% 8% 12% 32% 15% 1	4600
November	1st to 10th	Night	42% 8% 14% 21% 13% 2	2744
	11th to 20th	Night	36% 10% 15% 22% 16% 2	3041
	21st to end	Night	37% 9% 17% 22% 12% 4	3150
December	1st to 10th	Night	34% 11% 21% 22% 9% 3	5040
	11th to 20th	Night	40% 13% 19% 17% 10% 1	5697
	21st to end	Night	38% 9% 11% 22% 16% 4	7623

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 12% 33% 32% 13% 6%	220
	11th to 20th	Day	6% 13% 35% 34% 10% 2	220
	21st to end	Day	7% 15% 35% 31% 10% 2	242
February	1st to 10th	Day	9% 20% 36% 24% 7% 5%	220
	11th to 20th	Day	5% 13% 36% 36% 8% 1	313
	21st to end	Day	6% 23% 31% 30% 9% 1	430
March	1st to 10th	Day	8% 21% 38% 22% 9% 2	540
	11th to 20th	Day	8% 20% 37% 26% 7% 2	540
	21st to end	Day	11% 25% 34% 20% 8% 2	594
April	1st to 10th	Day	14% 21% 35% 23% 6% 1	540
	11th to 20th	Day	17% 19% 31% 23% 9% 2	532
	21st to end	Day	17% 22% 27% 21% 9% 3	540
May	1st to 10th	Day	19% 17% 25% 26% 9% 3	551
	11th to 20th	Day	17% 15% 22% 27% 14% 4	775
	21st to end	Day	21% 9% 23% 26% 17% 3	844
June	1st to 10th	Day	18% 14% 31% 26% 10% 2	780
	11th to 20th	Day	21% 14% 29% 24% 10% 2	780
	21st to end	Day	12% 11% 26% 32% 16% 4	780
July	1st to 10th	Day	12% 6% 26% 34% 18% 4	771
	11th to 20th	Day	11% 10% 29% 30% 17% 3	768
	21st to end	Day	7% 8% 31% 35% 15% 5%	730
August	1st to 10th	Day	12% 8% 29% 34% 13% 5%	567
	11th to 20th	Day	11% 7% 29% 34% 14% 5%	557
	21st to end	Day	11% 13% 27% 30% 15% 5%	627
September	1st to 10th	Day	14% 12% 28% 27% 13% 6%	570
	11th to 20th	Day	17% 10% 25% 31% 15% 2	543
	21st to end	Day	16% 18% 30% 25% 8% 2	530
October	1st to 10th	Day	13% 13% 31% 27% 12% 3	467
	11th to 20th	Day	12% 16% 32% 27% 11% 3	330
	21st to end	Day	14% 20% 34% 23% 7% 2	363
November	1st to 10th	Day	16% 18% 36% 24% 6% 1	330
	11th to 20th	Day	11% 15% 38% 26% 8% 2	275
	21st to end	Day	8% 15% 37% 23% 10% 6%	220
December	1st to 10th	Day	7% 11% 42% 27% 10% 3	220
	11th to 20th	Day	6% 16% 35% 33% 7% 3	220
	21st to end	Day	6% 10% 32% 38% 11% 3	242
January	1st to 10th	Night	8% 14% 44% 26% 7% 1	1050
	11th to 20th	Night	6% 14% 45% 27% 6% 1	999
	21st to end	Night	7% 16% 43% 27% 7% 1	924
February	1st to 10th	Night	5% 16% 37% 28% 11% 3	840
	11th to 20th	Night	7% 12% 36% 33% 10% 1	824
	21st to end	Night	6% 9% 40% 27% 16% 2	692
March	1st to 10th	Night	5% 11% 40% 30% 10% 3	840
	11th to 20th	Night	7% 12% 39% 30% 10% 1	840
	21st to end	Night	9% 12% 33% 33% 11% 3	924
April	1st to 10th	Night	11% 13% 33% 32% 10% 1	806
	11th to 20th	Night	15% 11% 35% 30% 9%	623
	21st to end	Night	13% 12% 31% 30% 13%	630
May	1st to 10th	Night	17% 10% 25% 32% 15% 1	503
	11th to 20th	Night	16% 6% 25% 33% 19% 1	414
	21st to end	Night	19% 5% 23% 31% 21% 1	455
June	1st to 10th	Night	18% 8% 25% 37% 12% 1	420
	11th to 20th	Night	19% 6% 30% 30% 14% 1	420
	21st to end	Night	11% 4 24% 35% 24% 1	420
July	1st to 10th	Night	12% 4 18% 41% 24% 1	410
	11th to 20th	Night	9% 4 24% 42% 19% 2	408
	21st to end	Night	7% 5% 18% 43% 25% 2	460
August	1st to 10th	Night	13% 2 14% 40% 28% 3	418
	11th to 20th	Night	9% 4 19% 41% 25% 3	569
	21st to end	Night	10% 5% 21% 42% 20% 2	693
September	1st to 10th	Night	13% 4 24% 35% 19% 5%	772
	11th to 20th	Night	17% 6% 17% 35% 20% 5%	812
	21st to end	Night	12% 9% 35% 30% 10% 4	800
October	1st to 10th	Night	13% 7% 31% 33% 14% 3	800
	11th to 20th	Night	11% 10% 35% 30% 12% 2	800
	21st to end	Night	7% 14% 39% 31% 8% 1	880
November	1st to 10th	Night	12% 12% 44% 24% 7% 1	899
	11th to 20th	Night	8% 17% 44% 26% 5% 1	1050
	21st to end	Night	6% 13% 45% 26% 8% 2	1050
December	1st to 10th	Night	6% 15% 42% 26% 9% 2	1050
	11th to 20th	Night	4 14% 45% 29% 7% 1	1050
	21st to end	Night	7% 12% 41% 29% 9% 2	1155

Page generated at 2026-09-11 02:11:54. Version ac07

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