Pincher Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pincher Creek clear sky chart from 2005-11-06 to 2024-09-29.

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% 7% 3 6% 4 4 4 4 6% 8% 45%	101386
	Night	5% 8% 3 7% 5% 4 5% 4 6% 8% 45%	96881
Transparency	Day	35% 6% 15% 26% 14% 3	101138
	Night	36% 7% 17% 25% 13% 3	96775
Seeing	Day	19% 18% 27% 22% 11% 3	15196
	Night	16% 19% 30% 24% 10% 1	24274

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 7% 4 11% 5% 4 4 5% 7% 11% 39%	2219
	11th to 20th	Day	2 9% 7% 10% 6% 7% 5% 5% 7% 10% 33%	2367
	21st to end	Day	2 7% 3 7% 5% 4 5% 3 7% 12% 46%	2794
February	1st to 10th	Day	3 10% 5% 11% 5% 6% 6% 3 7% 10% 34%	1557
	11th to 20th	Day	3 13% 4 10% 6% 4 5% 4 7% 9% 35%	1665
	21st to end	Day	2 10% 5% 12% 7% 4 4 3 7% 8% 37%	1557
March	1st to 10th	Day	1 7% 3 8% 5% 4 5% 5% 8% 11% 43%	3138
	11th to 20th	Day	3 10% 2 5% 3 3 4 3 7% 9% 51%	3458
	21st to end	Day	8% 16% 6% 11% 4 3 5% 4 6% 8% 30%	3855
April	1st to 10th	Day	5% 13% 4 8% 5% 4 5% 4 7% 10% 34%	2313
	11th to 20th	Day	8% 12% 3 9% 5% 4 5% 4 7% 7% 35%	2440
	21st to end	Day	10% 12% 3 7% 5% 4 4 5% 6% 9% 36%	2470
May	1st to 10th	Day	14% 16% 4 7% 4 4 4 4 5% 6% 30%	4156
	11th to 20th	Day	11% 7% 2 7% 6% 5% 6% 5% 8% 9% 34%	4654
	21st to end	Day	14% 7% 2 6% 5% 5% 5% 5% 7% 9% 35%	5161
June	1st to 10th	Day	12% 7% 3 7% 5% 5% 5% 4 6% 8% 37%	2850
	11th to 20th	Day	15% 7% 3 6% 5% 6% 6% 5% 7% 7% 32%	2850
	21st to end	Day	7% 4 2 5% 4 4 5% 5% 6% 8% 50%	2850
July	1st to 10th	Day	4 3 1 5% 4 4 4 3 6% 9% 57%	4740
	11th to 20th	Day	4 2 1 3 2 3 4 3 6% 8% 64%	4740
	21st to end	Day	2 2 1 3 2 3 3 3 5% 7% 70%	4868
August	1st to 10th	Day	10% 5% 2 5% 3 4 4 4 7% 8% 47%	4358
	11th to 20th	Day	5% 3 1 3 3 3 5% 4 6% 8% 59%	4028
	21st to end	Day	7% 3 1 3 2 3 3 3 5% 7% 61%	4521
September	1st to 10th	Day	11% 4 2 3 3 3 4 3 6% 7% 54%	2319
	11th to 20th	Day	10% 5% 2 5% 4 4 4 3 5% 8% 51%	2090
	21st to end	Day	10% 6% 1 4 3 4 3 3 5% 7% 54%	2069
October	1st to 10th	Day	12% 10% 3 5% 3 3 4 4 5% 7% 45%	1915
	11th to 20th	Day	5% 9% 3 6% 3 4 5% 4 6% 7% 48%	1690
	21st to end	Day	5% 10% 4 8% 4 4 4 4 6% 9% 42%	1782
November	1st to 10th	Day	7% 11% 3 7% 3 4 4 4 7% 10% 41%	1608
	11th to 20th	Day	3 9% 3 6% 3 4 4 4 7% 9% 48%	1520
	21st to end	Day	2 11% 5% 8% 6% 4 4 4 6% 9% 41%	1330
December	1st to 10th	Day	2 8% 4 7% 6% 4 4 5% 7% 8% 43%	1330
	11th to 20th	Day	4 9% 2 10% 5% 4 5% 4 8% 10% 39%	1682
	21st to end	Day	2 8% 3 7% 4 5% 4 3 6% 9% 48%	2442
January	1st to 10th	Night	2 8% 4 9% 5% 5% 5% 5% 8% 10% 39%	4726
	11th to 20th	Night	2 10% 5% 11% 6% 5% 7% 5% 6% 8% 35%	4559
	21st to end	Night	2 8% 3 8% 4 5% 5% 4 7% 9% 44%	4862
February	1st to 10th	Night	3 13% 4 11% 5% 5% 5% 4 6% 9% 35%	2622
	11th to 20th	Night	2 13% 4 9% 4 5% 6% 4 6% 9% 37%	2402
	21st to end	Night	2 9% 4 11% 7% 6% 5% 4 5% 6% 40%	1894
March	1st to 10th	Night	1 6% 4 12% 7% 7% 7% 4 6% 7% 39%	3736
	11th to 20th	Night	3 7% 3 6% 4 4 5% 4 6% 8% 52%	3508
	21st to end	Night	7% 19% 7% 10% 4 4 3 4 5% 7% 28%	3784
April	1st to 10th	Night	9% 10% 3 7% 4 4 5% 4 6% 8% 40%	1866
	11th to 20th	Night	9% 10% 4 7% 4 4 4 5% 7% 8% 38%	1691
	21st to end	Night	7% 11% 4 7% 6% 4 4 3 7% 7% 40%	1710
May	1st to 10th	Night	15% 14% 4 8% 5% 4 4 3 5% 6% 32%	2810
	11th to 20th	Night	8% 6% 3 6% 3 5% 4 4 7% 10% 43%	2237
	21st to end	Night	15% 7% 3 7% 5% 5% 6% 5% 7% 7% 33%	2414
June	1st to 10th	Night	11% 6% 2 6% 5% 4 4 4 6% 9% 42%	1330
	11th to 20th	Night	17% 6% 2 5% 4 5% 4 4 6% 8% 39%	1330
	21st to end	Night	5% 3 2 5% 4 4 5% 4 6% 8% 56%	1330
July	1st to 10th	Night	3 3 1 3 3 3 5% 4 6% 9% 60%	2220
	11th to 20th	Night	4 2 1 3 3 2 2 3 5% 7% 68%	2220
	21st to end	Night	3 2 1 3 3 3 2 2 4 5% 72%	2667
August	1st to 10th	Night	11% 4 2 4 3 3 4 3 5% 7% 54%	2560
	11th to 20th	Night	5% 3 1 4 4 4 5% 4 8% 10% 52%	2811
	21st to end	Night	5% 2 1 3 3 3 3 4 6% 7% 62%	3146
September	1st to 10th	Night	10% 4 1 4 3 3 4 3 5% 6% 58%	1857
	11th to 20th	Night	11% 6% 2 4 2 2 3 3 5% 7% 54%	2090
	21st to end	Night	10% 6% 2 3 3 3 3 3 5% 8% 55%	2079
October	1st to 10th	Night	12% 7% 2 4 3 3 3 4 5% 7% 50%	2044
	11th to 20th	Night	6% 6% 2 4 4 4 4 3 6% 8% 53%	2268
	21st to end	Night	5% 8% 3 7% 5% 4 4 4 7% 8% 43%	2574
November	1st to 10th	Night	6% 12% 3 7% 5% 5% 4 4 6% 8% 41%	2452
	11th to 20th	Night	2 7% 3 7% 4 3 5% 5% 7% 9% 48%	2660
	21st to end	Night	2 10% 4 7% 5% 4 5% 3 6% 10% 43%	2848
December	1st to 10th	Night	2 8% 3 8% 6% 4 5% 5% 6% 9% 43%	2850
	11th to 20th	Night	2 7% 4 9% 7% 5% 6% 5% 8% 9% 36%	3510
	21st to end	Night	1 8% 4 7% 5% 5% 5% 4 7% 8% 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% 10% 20% 22% 11% 1	2219
	11th to 20th	Day	46% 7% 18% 13% 13% 4	2390
	21st to end	Day	31% 8% 24% 29% 7% 1	2794
February	1st to 10th	Day	46% 6% 18% 21% 8% 2	1557
	11th to 20th	Day	44% 7% 19% 20% 9% 1	1674
	21st to end	Day	44% 8% 15% 21% 11% 1	1557
March	1st to 10th	Day	32% 9% 14% 27% 17% 1	3138
	11th to 20th	Day	29% 7% 22% 31% 10% 1	3459
	21st to end	Day	51% 8% 13% 22% 6%	3855
April	1st to 10th	Day	43% 7% 17% 23% 9% 1	2313
	11th to 20th	Day	45% 7% 15% 22% 10% 1	2440
	21st to end	Day	44% 7% 15% 21% 11% 1	2470
May	1st to 10th	Day	53% 4 11% 24% 7%	4156
	11th to 20th	Day	40% 10% 14% 26% 10% 1	4658
	21st to end	Day	42% 8% 15% 20% 14% 1	5162
June	1st to 10th	Day	43% 8% 14% 21% 12% 2	2850
	11th to 20th	Day	47% 6% 12% 20% 12% 2	2850
	21st to end	Day	30% 6% 16% 30% 14% 3	2850
July	1st to 10th	Day	25% 4 9% 30% 23% 9%	4666
	11th to 20th	Day	19% 4 8% 33% 25% 11%	4659
	21st to end	Day	15% 3 7% 28% 28% 19%	4714
August	1st to 10th	Day	34% 4 14% 25% 19% 5%	4341
	11th to 20th	Day	23% 3 19% 37% 15% 3	4067
	21st to end	Day	23% 4 10% 41% 20% 3	4520
September	1st to 10th	Day	29% 4 12% 28% 19% 8%	2319
	11th to 20th	Day	32% 6% 13% 29% 16% 4	2090
	21st to end	Day	30% 6% 14% 33% 14% 3	2069
October	1st to 10th	Day	37% 6% 18% 26% 11% 2	1915
	11th to 20th	Day	34% 7% 20% 24% 14% 2	1690
	21st to end	Day	38% 7% 17% 25% 11% 1	1782
November	1st to 10th	Day	38% 10% 17% 23% 11%	1608
	11th to 20th	Day	32% 9% 23% 25% 9% 2	1520
	21st to end	Day	38% 8% 22% 20% 9% 3	1330
December	1st to 10th	Day	37% 9% 22% 22% 8% 3	1330
	11th to 20th	Day	37% 10% 23% 23% 6% 1	1684
	21st to end	Day	32% 7% 17% 25% 19% 1	2442
January	1st to 10th	Night	37% 11% 20% 23% 8% 1	4726
	11th to 20th	Night	46% 7% 16% 16% 11% 5%	4598
	21st to end	Night	33% 9% 23% 26% 8% 1	4862
February	1st to 10th	Night	46% 8% 15% 18% 11% 2	2622
	11th to 20th	Night	42% 9% 19% 20% 10% 1	2403
	21st to end	Night	44% 6% 13% 25% 9% 2	1894
March	1st to 10th	Night	39% 10% 15% 22% 14% 1	3736
	11th to 20th	Night	28% 9% 25% 27% 10% 1	3508
	21st to end	Night	53% 8% 14% 19% 5%	3784
April	1st to 10th	Night	40% 8% 17% 25% 9% 1	1866
	11th to 20th	Night	41% 7% 14% 28% 9%	1691
	21st to end	Night	41% 7% 14% 28% 9% 1	1710
May	1st to 10th	Night	53% 5% 11% 24% 6%	2810
	11th to 20th	Night	32% 10% 12% 32% 15%	2237
	21st to end	Night	46% 8% 15% 20% 10%	2414
June	1st to 10th	Night	38% 6% 17% 27% 11% 1	1330
	11th to 20th	Night	43% 5% 16% 22% 13% 1	1330
	21st to end	Night	25% 5% 19% 31% 17% 3	1330
July	1st to 10th	Night	20% 4 16% 29% 23% 8%	2185
	11th to 20th	Night	16% 3 13% 31% 24% 13%	2178
	21st to end	Night	17% 2 8% 28% 28% 18%	2582
August	1st to 10th	Night	31% 3 15% 26% 17% 8%	2552
	11th to 20th	Night	27% 3 19% 33% 16% 2	2838
	21st to end	Night	21% 3 10% 40% 22% 3	3146
September	1st to 10th	Night	27% 5% 11% 31% 17% 8%	1857
	11th to 20th	Night	30% 4 15% 30% 17% 4	2090
	21st to end	Night	28% 4 18% 30% 16% 3	2079
October	1st to 10th	Night	34% 5% 18% 28% 15% 1	2044
	11th to 20th	Night	29% 7% 18% 29% 15% 3	2268
	21st to end	Night	37% 9% 18% 25% 11% 1	2574
November	1st to 10th	Night	40% 7% 20% 22% 10% 1	2452
	11th to 20th	Night	31% 8% 23% 24% 12% 1	2660
	21st to end	Night	37% 8% 22% 20% 10% 3	2848
December	1st to 10th	Night	37% 9% 20% 21% 11% 3	2850
	11th to 20th	Night	39% 11% 22% 21% 5% 1	3507
	21st to end	Night	35% 6% 20% 22% 14% 4	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	18% 22% 27% 18% 11% 4	180
	11th to 20th	Day	27% 16% 26% 23% 8% 2	180
	21st to end	Day	23% 32% 27% 9% 7% 3	198
February	1st to 10th	Day	28% 14% 31% 18% 8% 1	198
	11th to 20th	Day	21% 23% 26% 21% 9% 1	270
	21st to end	Day	20% 27% 30% 19% 4 1	369
March	1st to 10th	Day	20% 22% 29% 19% 7% 3	460
	11th to 20th	Day	18% 23% 25% 20% 12% 2	460
	21st to end	Day	24% 24% 27% 17% 7% 2	506
April	1st to 10th	Day	23% 25% 29% 17% 5%	460
	11th to 20th	Day	23% 23% 26% 17% 9% 2	452
	21st to end	Day	23% 24% 25% 19% 8% 1	460
May	1st to 10th	Day	19% 17% 28% 20% 12% 3	463
	11th to 20th	Day	25% 11% 24% 23% 14% 3	648
	21st to end	Day	26% 10% 22% 25% 14% 4	734
June	1st to 10th	Day	21% 18% 26% 23% 10% 2	680
	11th to 20th	Day	26% 19% 24% 20% 8% 3	680
	21st to end	Day	12% 12% 30% 27% 15% 4	680
July	1st to 10th	Day	11% 9% 28% 29% 19% 4	671
	11th to 20th	Day	11% 14% 26% 31% 15% 3	668
	21st to end	Day	8% 11% 32% 29% 16% 3	583
August	1st to 10th	Day	12% 10% 28% 31% 16% 3	487
	11th to 20th	Day	8% 9% 31% 29% 18% 5%	477
	21st to end	Day	14% 11% 34% 25% 13% 3	539
September	1st to 10th	Day	17% 18% 22% 22% 16% 4	490
	11th to 20th	Day	18% 11% 35% 21% 12% 3	490
	21st to end	Day	23% 24% 25% 18% 8% 2	483
October	1st to 10th	Day	22% 15% 26% 21% 13% 3	385
	11th to 20th	Day	18% 23% 28% 19% 10% 3	270
	21st to end	Day	26% 24% 25% 15% 8% 2	297
November	1st to 10th	Day	27% 26% 26% 14% 6% 1	270
	11th to 20th	Day	25% 25% 36% 13% 2	270
	21st to end	Day	23% 26% 21% 14% 9% 6%	180
December	1st to 10th	Day	19% 28% 31% 12% 7% 3	180
	11th to 20th	Day	28% 19% 27% 18% 6% 2	180
	21st to end	Day	21% 22% 22% 21% 10% 5%	198
January	1st to 10th	Night	21% 26% 32% 16% 5%	950
	11th to 20th	Night	17% 24% 38% 16% 4 1	860
	21st to end	Night	16% 29% 34% 15% 5% 1	836
February	1st to 10th	Night	17% 21% 31% 21% 7% 2	760
	11th to 20th	Night	18% 25% 29% 22% 7%	744
	21st to end	Night	15% 22% 31% 25% 7%	628
March	1st to 10th	Night	13% 22% 31% 24% 9% 2	760
	11th to 20th	Night	16% 20% 30% 25% 7% 1	760
	21st to end	Night	17% 18% 26% 26% 11% 1	836
April	1st to 10th	Night	16% 22% 27% 24% 10% 1	726
	11th to 20th	Night	16% 21% 27% 26% 9%	563
	21st to end	Night	17% 15% 34% 24% 10% 1	570
May	1st to 10th	Night	19% 16% 25% 25% 15%	546
	11th to 20th	Night	16% 8% 26% 32% 17% 2	374
	21st to end	Night	24% 10% 19% 30% 16% 1	411
June	1st to 10th	Night	19% 12% 26% 29% 12% 2	380
	11th to 20th	Night	23% 15% 27% 24% 10% 1	380
	21st to end	Night	7% 12% 33% 29% 17% 1	380
July	1st to 10th	Night	8% 6% 24% 38% 23%	370
	11th to 20th	Night	9% 5% 29% 42% 14% 1	368
	21st to end	Night	6% 5% 28% 40% 20% 1	416
August	1st to 10th	Night	10% 4 21% 40% 24% 1	396
	11th to 20th	Night	8% 6% 26% 37% 22% 1	564
	21st to end	Night	10% 8% 29% 37% 15% 1	627
September	1st to 10th	Night	13% 9% 26% 33% 17% 3	689
	11th to 20th	Night	16% 10% 25% 28% 17% 3	760
	21st to end	Night	16% 16% 30% 26% 10% 2	756
October	1st to 10th	Night	20% 11% 26% 26% 16% 1	720
	11th to 20th	Night	16% 19% 28% 27% 9% 1	720
	21st to end	Night	19% 23% 32% 18% 6% 1	792
November	1st to 10th	Night	24% 22% 29% 20% 4	787
	11th to 20th	Night	22% 29% 33% 13% 3 1	950
	21st to end	Night	16% 31% 31% 16% 5% 1	950
December	1st to 10th	Night	14% 28% 30% 20% 6% 1	950
	11th to 20th	Night	17% 24% 34% 19% 5%	950
	21st to end	Night	18% 23% 34% 17% 7% 1	1045

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