High River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High River clear sky chart from 2005-11-06 to 2024-11-05.

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% 8% 3 7% 5% 5% 5% 4 6% 8% 41%	105585
	Night	6% 9% 3 8% 5% 5% 5% 4 6% 8% 40%	102045
Transparency	Day	39% 7% 15% 26% 12% 2	105331
	Night	40% 7% 14% 24% 12% 2	101945
Seeing	Day	13% 13% 31% 27% 13% 4	15359
	Night	11% 9% 31% 33% 13% 2	24419

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	2 10% 6% 11% 6% 5% 4 4 8% 8% 35%	2219
	11th to 20th	Day	3 9% 4 10% 7% 6% 5% 6% 8% 7% 37%	2272
	21st to end	Day	3 8% 3 9% 6% 5% 6% 4 5% 9% 41%	2794
February	1st to 10th	Day	3 11% 5% 12% 7% 5% 7% 4 8% 8% 30%	1528
	11th to 20th	Day	4 11% 6% 10% 7% 6% 6% 5% 7% 9% 29%	1665
	21st to end	Day	2 11% 6% 12% 7% 6% 6% 4 6% 8% 32%	1532
March	1st to 10th	Day	2 9% 4 12% 8% 6% 6% 4 6% 7% 36%	3138
	11th to 20th	Day	6% 9% 3 7% 4 4 4 3 5% 8% 48%	3457
	21st to end	Day	8% 20% 6% 13% 5% 4 4 4 5% 6% 25%	3872
April	1st to 10th	Day	9% 14% 4 9% 5% 6% 5% 4 7% 7% 30%	2330
	11th to 20th	Day	9% 14% 4 9% 5% 5% 5% 4 6% 8% 32%	2440
	21st to end	Day	11% 11% 3 8% 5% 5% 4 5% 7% 8% 33%	2470
May	1st to 10th	Day	18% 14% 4 7% 4 4 4 3 5% 7% 29%	4271
	11th to 20th	Day	10% 7% 3 9% 6% 6% 6% 5% 8% 8% 32%	4694
	21st to end	Day	15% 8% 3 9% 7% 7% 6% 5% 6% 7% 26%	5161
June	1st to 10th	Day	15% 8% 3 7% 6% 5% 6% 5% 8% 7% 30%	2850
	11th to 20th	Day	19% 9% 3 7% 5% 5% 5% 4 6% 8% 28%	2850
	21st to end	Day	8% 5% 2 6% 4 5% 6% 4 8% 9% 43%	2850
July	1st to 10th	Day	6% 4 1 5% 4 4 5% 4 6% 8% 51%	4740
	11th to 20th	Day	5% 3 1 4 3 3 4 4 7% 10% 55%	4740
	21st to end	Day	2 3 1 3 3 4 4 3 6% 8% 62%	4987
August	1st to 10th	Day	9% 5% 2 5% 3 4 4 5% 7% 11% 44%	4401
	11th to 20th	Day	7% 5% 2 4 4 4 4 6% 7% 9% 48%	4037
	21st to end	Day	9% 3 1 4 3 3 4 3 6% 8% 55%	4521
September	1st to 10th	Day	10% 5% 2 5% 3 4 4 3 5% 7% 52%	2345
	11th to 20th	Day	13% 7% 2 4 3 3 5% 4 5% 9% 45%	2090
	21st to end	Day	8% 8% 2 7% 4 4 4 3 6% 10% 45%	2090
October	1st to 10th	Day	7% 6% 2 7% 5% 4 4 4 6% 10% 45%	3344
	11th to 20th	Day	5% 7% 2 7% 4 4 4 3 8% 11% 45%	2937
	21st to end	Day	6% 8% 3 6% 5% 5% 5% 4 5% 8% 45%	3101
November	1st to 10th	Day	8% 14% 4 9% 5% 4 5% 4 5% 7% 35%	1601
	11th to 20th	Day	5% 11% 3 8% 5% 5% 4 4 7% 8% 41%	1474
	21st to end	Day	4 11% 5% 8% 5% 4 4 5% 7% 10% 37%	1330
December	1st to 10th	Day	4 11% 4 10% 6% 6% 6% 4 6% 6% 37%	1330
	11th to 20th	Day	3 11% 6% 11% 8% 6% 5% 5% 7% 6% 33%	1682
	21st to end	Day	3 8% 3 8% 4 5% 5% 4 5% 10% 45%	2442
January	1st to 10th	Night	3 11% 5% 12% 7% 7% 6% 5% 7% 8% 29%	4726
	11th to 20th	Night	3 7% 5% 14% 6% 5% 6% 6% 6% 8% 34%	4656
	21st to end	Night	4 11% 4 10% 5% 5% 4 3 6% 7% 40%	4862
February	1st to 10th	Night	4 11% 4 11% 6% 6% 5% 5% 7% 8% 33%	2651
	11th to 20th	Night	4 14% 6% 10% 6% 5% 6% 4 7% 8% 32%	2402
	21st to end	Night	3 10% 6% 11% 9% 6% 5% 4 4 6% 36%	1918
March	1st to 10th	Night	2 9% 5% 14% 8% 7% 6% 5% 6% 8% 30%	3736
	11th to 20th	Night	4 8% 3 6% 5% 4 5% 4 7% 8% 46%	3521
	21st to end	Night	10% 22% 6% 12% 6% 4 4 3 5% 6% 22%	3779
April	1st to 10th	Night	9% 14% 4 9% 5% 5% 5% 4 6% 8% 32%	1849
	11th to 20th	Night	9% 12% 4 9% 6% 5% 5% 4 6% 7% 32%	1691
	21st to end	Night	11% 10% 3 8% 6% 5% 6% 4 5% 8% 35%	1710
May	1st to 10th	Night	17% 13% 4 8% 5% 5% 4 3 4 7% 31%	2690
	11th to 20th	Night	10% 7% 3 7% 5% 5% 6% 5% 7% 11% 35%	2199
	21st to end	Night	15% 7% 3 8% 7% 6% 5% 5% 6% 8% 31%	2414
June	1st to 10th	Night	13% 8% 2 8% 5% 3 5% 4 6% 8% 37%	1330
	11th to 20th	Night	18% 7% 3 7% 5% 3 5% 5% 6% 9% 32%	1330
	21st to end	Night	6% 5% 2 5% 3 4 4 5% 9% 9% 48%	1330
July	1st to 10th	Night	5% 5% 2 7% 5% 5% 4 4 5% 8% 50%	2220
	11th to 20th	Night	4 3 1 4 3 4 5% 4 8% 10% 54%	2220
	21st to end	Night	4 2 1 4 3 3 3 3 6% 8% 62%	2561
August	1st to 10th	Night	8% 6% 2 6% 5% 5% 5% 5% 7% 8% 44%	2529
	11th to 20th	Night	5% 5% 2 8% 5% 6% 5% 4 6% 10% 45%	2801
	21st to end	Night	8% 3 2 4 3 4 3 3 6% 8% 57%	3146
September	1st to 10th	Night	9% 5% 2 5% 4 3 3 3 6% 7% 52%	1833
	11th to 20th	Night	14% 6% 2 5% 3 3 2 3 5% 7% 51%	2090
	21st to end	Night	9% 7% 2 4 3 5% 3 4 6% 8% 48%	2090
October	1st to 10th	Night	6% 5% 2 6% 4 3 5% 4 6% 8% 52%	3631
	11th to 20th	Night	6% 6% 2 5% 4 4 4 4 6% 9% 50%	3988
	21st to end	Night	5% 8% 3 7% 5% 5% 5% 4 6% 7% 47%	4457
November	1st to 10th	Night	7% 13% 3 8% 5% 5% 6% 4 5% 8% 36%	2559
	11th to 20th	Night	4 9% 3 8% 5% 5% 4 4 7% 8% 42%	2702
	21st to end	Night	4 11% 4 8% 5% 4 4 4 6% 10% 40%	2850
December	1st to 10th	Night	4 10% 4 9% 6% 6% 7% 4 6% 8% 35%	2850
	11th to 20th	Night	2 9% 4 12% 7% 6% 5% 5% 8% 8% 35%	3510
	21st to end	Night	4 9% 3 8% 5% 5% 5% 4 6% 8% 44%	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	43% 7% 13% 24% 10% 3	2219
	11th to 20th	Day	45% 5% 10% 18% 18% 4	2293
	21st to end	Day	37% 6% 15% 31% 9% 1	2794
February	1st to 10th	Day	49% 7% 15% 17% 9% 2	1528
	11th to 20th	Day	49% 7% 13% 20% 8% 2	1674
	21st to end	Day	49% 5% 13% 19% 13% 1	1532
March	1st to 10th	Day	47% 7% 13% 19% 14% 1	3138
	11th to 20th	Day	34% 6% 16% 28% 15% 1	3458
	21st to end	Day	58% 8% 11% 18% 5%	3872
April	1st to 10th	Day	51% 6% 14% 20% 8% 1	2330
	11th to 20th	Day	48% 6% 11% 22% 10% 2	2440
	21st to end	Day	47% 7% 13% 22% 10% 1	2470
May	1st to 10th	Day	54% 5% 10% 24% 6%	4271
	11th to 20th	Day	43% 8% 15% 24% 10%	4698
	21st to end	Day	53% 8% 13% 16% 8% 1	5162
June	1st to 10th	Day	47% 9% 15% 18% 9% 2	2850
	11th to 20th	Day	51% 8% 14% 17% 8% 2	2850
	21st to end	Day	33% 8% 19% 26% 11% 3	2850
July	1st to 10th	Day	27% 7% 15% 29% 17% 5%	4666
	11th to 20th	Day	23% 7% 19% 34% 16% 2	4659
	21st to end	Day	19% 5% 11% 29% 24% 12%	4829
August	1st to 10th	Day	31% 8% 15% 36% 8% 1	4384
	11th to 20th	Day	29% 8% 24% 30% 8% 2	4076
	21st to end	Day	26% 5% 16% 37% 14% 2	4520
September	1st to 10th	Day	31% 5% 14% 26% 17% 6%	2345
	11th to 20th	Day	37% 6% 14% 28% 13% 2	2090
	21st to end	Day	34% 6% 13% 30% 13% 3	2090
October	1st to 10th	Day	34% 6% 15% 36% 8% 1	3344
	11th to 20th	Day	31% 5% 20% 27% 14% 3	2937
	21st to end	Day	37% 6% 10% 33% 11% 2	3101
November	1st to 10th	Day	49% 6% 12% 19% 12% 2	1601
	11th to 20th	Day	41% 5% 17% 25% 11% 1	1474
	21st to end	Day	41% 6% 17% 23% 10% 3	1330
December	1st to 10th	Day	46% 6% 14% 19% 12% 4	1330
	11th to 20th	Day	49% 7% 15% 21% 7% 1	1684
	21st to end	Day	35% 6% 11% 25% 19% 5%	2442
January	1st to 10th	Night	49% 8% 12% 22% 7% 2	4726
	11th to 20th	Night	46% 6% 12% 16% 14% 5%	4697
	21st to end	Night	41% 6% 14% 25% 12% 1	4862
February	1st to 10th	Night	47% 7% 12% 21% 11% 3	2651
	11th to 20th	Night	49% 5% 13% 20% 11% 1	2403
	21st to end	Night	49% 5% 10% 22% 11% 3	1918
March	1st to 10th	Night	49% 8% 11% 22% 10% 1	3736
	11th to 20th	Night	33% 8% 19% 23% 15% 1	3521
	21st to end	Night	62% 6% 11% 15% 5% 1	3779
April	1st to 10th	Night	49% 7% 11% 21% 11% 1	1849
	11th to 20th	Night	49% 6% 12% 22% 9% 1	1691
	21st to end	Night	45% 8% 14% 22% 9% 2	1710
May	1st to 10th	Night	53% 7% 10% 23% 7%	2690
	11th to 20th	Night	39% 10% 12% 30% 8% 1	2199
	21st to end	Night	48% 10% 15% 18% 8% 1	2414
June	1st to 10th	Night	42% 8% 15% 23% 12% 1	1330
	11th to 20th	Night	47% 7% 15% 20% 8% 3	1330
	21st to end	Night	28% 8% 22% 27% 13% 1	1330
July	1st to 10th	Night	32% 6% 16% 23% 19% 3	2185
	11th to 20th	Night	22% 8% 21% 34% 11% 3	2178
	21st to end	Night	20% 5% 11% 31% 22% 10%	2480
August	1st to 10th	Night	34% 8% 16% 27% 14% 2	2521
	11th to 20th	Night	33% 8% 21% 27% 10% 1	2828
	21st to end	Night	24% 5% 18% 36% 15% 3	3146
September	1st to 10th	Night	30% 5% 15% 27% 17% 6%	1833
	11th to 20th	Night	32% 6% 15% 28% 14% 5%	2090
	21st to end	Night	33% 4 16% 27% 14% 4	2090
October	1st to 10th	Night	29% 6% 14% 29% 20% 2	3631
	11th to 20th	Night	31% 5% 19% 24% 18% 3	3988
	21st to end	Night	35% 5% 12% 32% 15% 1	4457
November	1st to 10th	Night	46% 6% 12% 21% 12% 2	2559
	11th to 20th	Night	39% 6% 16% 22% 16% 1	2702
	21st to end	Night	39% 6% 17% 23% 12% 4	2850
December	1st to 10th	Night	44% 7% 15% 20% 11% 4	2850
	11th to 20th	Night	42% 9% 18% 23% 7% 1	3507
	21st to end	Night	38% 5% 11% 28% 14% 5%	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% 33% 28% 16% 8%	180
	11th to 20th	Day	9% 14% 31% 30% 12% 4	180
	21st to end	Day	9% 10% 31% 38% 9% 4	198
February	1st to 10th	Day	11% 13% 39% 27% 8% 3	184
	11th to 20th	Day	6% 14% 36% 31% 11% 1	270
	21st to end	Day	8% 16% 36% 28% 11% 1	344
March	1st to 10th	Day	8% 21% 40% 18% 9% 3	460
	11th to 20th	Day	8% 19% 33% 27% 11% 2	460
	21st to end	Day	13% 23% 32% 20% 8% 4	506
April	1st to 10th	Day	18% 20% 35% 19% 7% 1	460
	11th to 20th	Day	16% 16% 34% 23% 9% 2	452
	21st to end	Day	17% 20% 31% 22% 8% 2	460
May	1st to 10th	Day	19% 14% 25% 26% 11% 5%	487
	11th to 20th	Day	18% 10% 25% 27% 16% 4	675
	21st to end	Day	19% 9% 23% 28% 17% 3	734
June	1st to 10th	Day	16% 13% 31% 26% 12% 2	680
	11th to 20th	Day	19% 13% 30% 24% 11% 3	680
	21st to end	Day	10% 10% 30% 30% 15% 5%	680
July	1st to 10th	Day	9% 6% 27% 33% 21% 3	671
	11th to 20th	Day	10% 9% 28% 31% 19% 3	668
	21st to end	Day	6% 9% 32% 30% 19% 4	650
August	1st to 10th	Day	10% 8% 31% 33% 14% 4	487
	11th to 20th	Day	8% 6% 30% 33% 17% 6%	477
	21st to end	Day	10% 10% 32% 25% 15% 7%	539
September	1st to 10th	Day	12% 12% 31% 26% 13% 6%	490
	11th to 20th	Day	17% 11% 26% 27% 13% 5%	490
	21st to end	Day	14% 18% 27% 27% 11% 3	490
October	1st to 10th	Day	15% 11% 26% 28% 16% 4	409
	11th to 20th	Day	12% 13% 33% 24% 13% 5%	300
	21st to end	Day	12% 17% 35% 25% 8% 3	330
November	1st to 10th	Day	20% 11% 33% 24% 8% 4	282
	11th to 20th	Day	12% 18% 33% 28% 8% 2	248
	21st to end	Day	9% 14% 33% 23% 11% 9%	180
December	1st to 10th	Day	9% 11% 34% 28% 15% 3	180
	11th to 20th	Day	7% 12% 43% 24% 9% 4	180
	21st to end	Day	9% 7% 29% 29% 20% 6%	198
January	1st to 10th	Night	9% 13% 33% 33% 11% 2	950
	11th to 20th	Night	8% 10% 36% 33% 11% 1	920
	21st to end	Night	10% 11% 32% 36% 10% 1	836
February	1st to 10th	Night	9% 13% 32% 31% 12% 3	760
	11th to 20th	Night	11% 9% 33% 34% 12% 1	744
	21st to end	Night	7% 7% 31% 35% 16% 3	628
March	1st to 10th	Night	9% 8% 36% 31% 13% 3	760
	11th to 20th	Night	9% 13% 34% 32% 11% 1	760
	21st to end	Night	13% 9% 33% 32% 9% 3	836
April	1st to 10th	Night	15% 12% 32% 28% 12% 1	709
	11th to 20th	Night	15% 10% 35% 30% 9%	563
	21st to end	Night	16% 11% 31% 30% 11% 1	570
May	1st to 10th	Night	16% 10% 26% 32% 15%	504
	11th to 20th	Night	13% 10% 22% 34% 20% 1	374
	21st to end	Night	22% 4 23% 34% 16% 1	411
June	1st to 10th	Night	14% 9% 31% 29% 14% 2	380
	11th to 20th	Night	22% 6% 29% 30% 12% 1	380
	21st to end	Night	9% 6% 22% 41% 21% 2	380
July	1st to 10th	Night	11% 4 19% 41% 25% 1	370
	11th to 20th	Night	9% 3 22% 43% 21% 2	368
	21st to end	Night	7% 4 24% 41% 22% 3	416
August	1st to 10th	Night	11% 5% 15% 39% 28% 2	378
	11th to 20th	Night	8% 3 21% 43% 22% 1	554
	21st to end	Night	11% 5% 25% 37% 20% 1	627
September	1st to 10th	Night	12% 5% 25% 37% 20% 3	670
	11th to 20th	Night	17% 5% 22% 35% 19% 2	760
	21st to end	Night	11% 8% 33% 34% 11% 3	760
October	1st to 10th	Night	15% 5% 26% 36% 15% 3	760
	11th to 20th	Night	12% 8% 31% 30% 15% 3	760
	21st to end	Night	12% 8% 33% 34% 11% 1	836
November	1st to 10th	Night	14% 11% 36% 29% 9% 1	850
	11th to 20th	Night	10% 15% 38% 29% 6% 1	950
	21st to end	Night	10% 10% 38% 31% 10% 2	950
December	1st to 10th	Night	8% 11% 34% 33% 11% 4	950
	11th to 20th	Night	5% 12% 38% 34% 10% 1	950
	21st to end	Night	11% 8% 34% 33% 12% 2	1045

Page generated at 2024-11-03 00:11:29. Version ac07

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