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 2024-11-01.

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	8% 9% 3 8% 5% 5% 5% 4 7% 8% 38%	101861
	Night	5% 9% 3 8% 5% 5% 5% 4 6% 8% 41%	97156
Transparency	Day	39% 10% 15% 22% 11% 2	101609
	Night	37% 10% 15% 23% 12% 3	97054
Seeing	Day	13% 14% 30% 28% 12% 3	15314
	Night	10% 11% 34% 31% 12% 2	24327

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 6% 4 12% 6% 6% 5% 4 9% 9% 38%	2219
	11th to 20th	Day	1 6% 3 11% 6% 7% 7% 5% 8% 7% 39%	2299
	21st to end	Day	1 8% 3 8% 5% 5% 5% 4 7% 9% 44%	2794
February	1st to 10th	Day	1 9% 4 10% 7% 6% 7% 6% 7% 8% 35%	1520
	11th to 20th	Day	1 9% 4 10% 7% 7% 7% 5% 8% 9% 34%	1632
	21st to end	Day	1 10% 5% 14% 6% 6% 6% 5% 6% 7% 33%	1555
March	1st to 10th	Day	1 7% 4 11% 7% 7% 8% 5% 7% 7% 36%	3138
	11th to 20th	Day	3 10% 2 7% 4 3 4 3 6% 8% 48%	3418
	21st to end	Day	4 19% 7% 17% 5% 5% 4 4 5% 6% 24%	3931
April	1st to 10th	Day	7% 16% 4 9% 7% 6% 4 5% 6% 8% 28%	2309
	11th to 20th	Day	9% 16% 6% 9% 5% 5% 4 3 6% 7% 30%	2440
	21st to end	Day	11% 14% 4 8% 5% 5% 4 5% 6% 7% 32%	2470
May	1st to 10th	Day	16% 17% 4 8% 5% 5% 4 3 5% 5% 27%	4315
	11th to 20th	Day	10% 11% 3 9% 6% 5% 5% 5% 7% 8% 29%	4694
	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	9% 10% 3 6% 4 4 4 4 6% 7% 41%	2030
	11th to 20th	Day	6% 10% 3 9% 5% 5% 5% 4 6% 9% 40%	1731
	21st to end	Day	5% 10% 4 8% 5% 4 5% 4 7% 8% 40%	1881
November	1st to 10th	Day	5% 13% 4 9% 6% 5% 6% 4 7% 6% 36%	1584
	11th to 20th	Day	3 9% 4 7% 6% 5% 4 4 6% 7% 45%	1425
	21st to end	Day	2 10% 5% 9% 6% 4 4 4 7% 7% 42%	1330
December	1st to 10th	Day	2 8% 4 10% 7% 6% 5% 4 8% 9% 38%	1330
	11th to 20th	Day	2 6% 4 13% 6% 7% 6% 5% 7% 10% 33%	1682
	21st to end	Day	3 8% 3 8% 5% 4 5% 4 6% 8% 46%	2442
January	1st to 10th	Night	1 9% 5% 10% 7% 7% 6% 5% 7% 9% 32%	4726
	11th to 20th	Night	1 6% 3 12% 7% 6% 7% 5% 7% 8% 37%	4628
	21st to end	Night	2 9% 4 10% 7% 6% 5% 4 6% 8% 39%	4862
February	1st to 10th	Night	2 8% 3 9% 6% 6% 7% 5% 7% 9% 36%	2660
	11th to 20th	Night	2 11% 5% 10% 7% 5% 5% 4 5% 9% 36%	2434
	21st to end	Night	1 8% 4 11% 8% 6% 5% 4 5% 7% 39%	1897
March	1st to 10th	Night	1 6% 4 11% 8% 8% 7% 5% 8% 8% 34%	3736
	11th to 20th	Night	3 9% 2 6% 4 4 5% 4 6% 9% 49%	3561
	21st to end	Night	7% 19% 6% 13% 6% 6% 4 4 5% 6% 25%	3719
April	1st to 10th	Night	6% 15% 5% 9% 6% 3 5% 4 7% 7% 35%	1870
	11th to 20th	Night	8% 14% 5% 10% 5% 4 3 3 6% 7% 34%	1691
	21st to end	Night	7% 14% 3 8% 5% 4 5% 4 6% 8% 36%	1710
May	1st to 10th	Night	16% 17% 3 7% 4 4 4 3 5% 6% 31%	2632
	11th to 20th	Night	10% 9% 3 7% 6% 4 5% 4 6% 10% 35%	2199
	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	9% 9% 2 6% 4 4 4 4 5% 7% 45%	2149
	11th to 20th	Night	7% 8% 3 6% 4 4 3 4 7% 8% 46%	2446
	21st to end	Night	4 9% 3 9% 5% 5% 5% 4 6% 8% 42%	2717
November	1st to 10th	Night	3 13% 4 8% 6% 4 5% 4 7% 7% 39%	2482
	11th to 20th	Night	3 8% 3 8% 5% 5% 5% 5% 6% 8% 45%	2751
	21st to end	Night	2 9% 4 9% 6% 5% 5% 5% 6% 9% 41%	2850
December	1st to 10th	Night	2 9% 4 9% 6% 5% 6% 4 7% 10% 37%	2850
	11th to 20th	Night	1 7% 4 11% 7% 6% 6% 6% 8% 8% 36%	3510
	21st to end	Night	2 8% 3 9% 5% 5% 5% 5% 6% 7% 45%	5214

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	37% 9% 15% 25% 11% 3	2219
	11th to 20th	Day	39% 9% 10% 19% 20% 4	2320
	21st to end	Day	32% 12% 16% 29% 9% 1	2794
February	1st to 10th	Day	42% 13% 13% 19% 10% 4	1520
	11th to 20th	Day	42% 10% 16% 19% 10% 2	1641
	21st to end	Day	47% 9% 14% 15% 13% 1	1555
March	1st to 10th	Day	38% 15% 14% 18% 14% 1	3138
	11th to 20th	Day	32% 8% 19% 27% 12% 1	3419
	21st to end	Day	57% 11% 13% 15% 5%	3931
April	1st to 10th	Day	49% 10% 17% 15% 8% 1	2309
	11th to 20th	Day	52% 8% 13% 17% 9% 1	2440
	21st to end	Day	49% 9% 15% 19% 7% 1	2470
May	1st to 10th	Day	57% 7% 11% 20% 5%	4315
	11th to 20th	Day	43% 13% 14% 21% 9%	4698
	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	40% 9% 15% 23% 11% 1	2030
	11th to 20th	Day	38% 10% 17% 22% 11% 3	1731
	21st to end	Day	39% 10% 14% 22% 14% 2	1881
November	1st to 10th	Day	44% 10% 13% 19% 12% 1	1584
	11th to 20th	Day	35% 10% 17% 25% 12% 2	1425
	21st to end	Day	38% 9% 18% 22% 10% 4	1330
December	1st to 10th	Day	39% 10% 16% 18% 13% 4	1330
	11th to 20th	Day	39% 14% 16% 19% 10% 1	1684
	21st to end	Day	33% 8% 10% 25% 19% 5%	2442
January	1st to 10th	Night	41% 13% 15% 20% 8% 2	4726
	11th to 20th	Night	40% 10% 12% 16% 15% 6%	4669
	21st to end	Night	36% 13% 15% 22% 13% 1	4862
February	1st to 10th	Night	40% 12% 12% 20% 13% 3	2660
	11th to 20th	Night	43% 9% 16% 18% 13% 2	2435
	21st to end	Night	43% 7% 11% 21% 14% 3	1897
March	1st to 10th	Night	39% 13% 14% 21% 13% 1	3736
	11th to 20th	Night	29% 10% 19% 25% 16% 1	3561
	21st to end	Night	53% 13% 11% 16% 6% 1	3719
April	1st to 10th	Night	45% 9% 14% 20% 11% 1	1870
	11th to 20th	Night	48% 8% 12% 22% 9% 1	1691
	21st to end	Night	44% 9% 15% 21% 8% 2	1710
May	1st to 10th	Night	53% 7% 11% 22% 6%	2632
	11th to 20th	Night	39% 10% 15% 28% 8% 1	2199
	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	37% 9% 13% 24% 15% 2	2149
	11th to 20th	Night	33% 8% 19% 24% 13% 3	2446
	21st to end	Night	38% 9% 15% 24% 12% 1	2717
November	1st to 10th	Night	43% 8% 14% 20% 13% 2	2482
	11th to 20th	Night	35% 9% 15% 22% 17% 2	2751
	21st to end	Night	37% 9% 17% 21% 12% 4	2850
December	1st to 10th	Night	40% 10% 14% 21% 11% 4	2850
	11th to 20th	Night	37% 16% 17% 21% 8% 1	3507
	21st to end	Night	34% 10% 13% 22% 15% 6%	5214

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	3 12% 32% 31% 14% 7%	180
	11th to 20th	Day	7% 9% 37% 33% 12% 2	180
	21st to end	Day	8% 15% 33% 31% 11% 3	198
February	1st to 10th	Day	9% 20% 34% 23% 8% 5%	180
	11th to 20th	Day	5% 15% 35% 35% 9% 1	255
	21st to end	Day	4 22% 29% 33% 10% 1	367
March	1st to 10th	Day	7% 20% 40% 22% 8% 2	460
	11th to 20th	Day	7% 20% 35% 27% 8% 2	460
	21st to end	Day	12% 24% 31% 21% 9% 3	506
April	1st to 10th	Day	13% 22% 36% 23% 5% 1	460
	11th to 20th	Day	17% 17% 31% 23% 10% 2	452
	21st to end	Day	18% 22% 28% 21% 10% 2	460
May	1st to 10th	Day	21% 16% 24% 25% 10% 4	470
	11th to 20th	Day	18% 13% 22% 28% 15% 4	675
	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% 33% 23% 8% 3	330
November	1st to 10th	Day	16% 17% 37% 22% 6% 1	270
	11th to 20th	Day	12% 15% 39% 25% 8% 1	225
	21st to end	Day	8% 17% 37% 22% 9% 8%	180
December	1st to 10th	Day	4 12% 43% 26% 11% 4	180
	11th to 20th	Day	4 16% 35% 35% 7% 3	180
	21st to end	Day	6% 10% 31% 37% 13% 4	198
January	1st to 10th	Night	8% 15% 42% 27% 7% 1	950
	11th to 20th	Night	6% 13% 44% 28% 7% 1	905
	21st to end	Night	7% 16% 42% 26% 8% 1	836
February	1st to 10th	Night	5% 17% 37% 26% 12% 3	760
	11th to 20th	Night	7% 13% 36% 31% 11% 1	744
	21st to end	Night	6% 9% 38% 27% 17% 3	628
March	1st to 10th	Night	4 11% 41% 30% 11% 3	760
	11th to 20th	Night	7% 12% 39% 30% 11% 2	760
	21st to end	Night	9% 12% 31% 33% 11% 3	836
April	1st to 10th	Night	11% 12% 33% 32% 10% 2	730
	11th to 20th	Night	16% 11% 34% 30% 10%	563
	21st to end	Night	14% 12% 31% 31% 12% 1	570
May	1st to 10th	Night	18% 11% 24% 31% 16% 1	455
	11th to 20th	Night	16% 6% 25% 33% 19% 1	374
	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% 12% 43% 24% 8% 1	813
	11th to 20th	Night	9% 17% 44% 25% 4 1	950
	21st to end	Night	6% 14% 46% 24% 8% 2	950
December	1st to 10th	Night	7% 15% 40% 27% 9% 2	950
	11th to 20th	Night	4 13% 44% 30% 7% 1	950
	21st to end	Night	7% 12% 40% 30% 9% 2	1045

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