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 2024-04-25.

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% 6% 4 5% 5% 6% 8% 39%	82744
	Night	6% 9% 4 8% 6% 4 5% 5% 6% 8% 39%	86379
Transparency	Day	41% 7% 15% 24% 11% 2	82451
	Night	42% 7% 14% 23% 12% 2	86252
Seeing	Day	13% 13% 31% 27% 13% 4	14535
	Night	11% 9% 31% 33% 13% 2	23871

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% 7% 10% 7% 3 5% 5% 8% 9% 35%	2219
	11th to 20th	Day	4 8% 4 8% 8% 4 6% 7% 7% 7% 37%	2272
	21st to end	Day	3 8% 3 8% 7% 4 5% 6% 5% 10% 41%	2794
February	1st to 10th	Day	4 10% 5% 10% 9% 4 7% 6% 7% 8% 30%	1528
	11th to 20th	Day	4 10% 6% 9% 8% 5% 6% 6% 7% 9% 29%	1665
	21st to end	Day	3 10% 7% 11% 8% 4 7% 5% 6% 9% 32%	1532
March	1st to 10th	Day	2 9% 5% 10% 10% 5% 6% 5% 5% 7% 36%	3138
	11th to 20th	Day	6% 8% 3 6% 4 3 5% 4 5% 8% 48%	3457
	21st to end	Day	8% 20% 7% 12% 6% 3 4 5% 4 7% 25%	3872
April	1st to 10th	Day	10% 13% 5% 8% 7% 5% 5% 5% 7% 7% 30%	2330
	11th to 20th	Day	9% 13% 5% 7% 6% 4 4 5% 6% 8% 32%	2440
	21st to end	Day	11% 11% 3 7% 6% 4 5% 6% 6% 8% 34%	2394
May	1st to 10th	Day	13% 10% 4 8% 7% 4 6% 6% 6% 8% 29%	2421
	11th to 20th	Day	13% 7% 3 7% 5% 4 6% 5% 6% 8% 36%	2654
	21st to end	Day	20% 7% 3 6% 6% 4 6% 5% 6% 7% 30%	2917
June	1st to 10th	Day	16% 7% 3 7% 7% 3 6% 6% 8% 8% 29%	2700
	11th to 20th	Day	20% 8% 3 7% 6% 4 5% 6% 6% 8% 28%	2700
	21st to end	Day	8% 4 2 5% 5% 4 6% 6% 7% 9% 43%	2700
July	1st to 10th	Day	8% 5% 2 4 5% 3 6% 6% 7% 9% 44%	2700
	11th to 20th	Day	8% 5% 2 4 4 3 5% 5% 6% 8% 49%	2700
	21st to end	Day	3 4 1 4 4 3 5% 5% 6% 8% 56%	2854
August	1st to 10th	Day	9% 5% 2 3 4 3 4 6% 6% 10% 48%	2507
	11th to 20th	Day	9% 4 1 3 4 3 4 6% 6% 8% 51%	2308
	21st to end	Day	9% 4 2 4 4 2 4 5% 6% 9% 51%	2574
September	1st to 10th	Day	11% 6% 2 4 4 3 4 4 5% 7% 51%	2223
	11th to 20th	Day	13% 7% 2 4 4 2 5% 5% 5% 9% 45%	1980
	21st to end	Day	8% 8% 2 6% 5% 3 4 4 5% 10% 45%	1980
October	1st to 10th	Day	12% 8% 3 7% 5% 3 4 4 6% 8% 40%	1904
	11th to 20th	Day	8% 8% 3 7% 7% 4 4 4 6% 9% 40%	1676
	21st to end	Day	7% 10% 3 6% 6% 4 6% 5% 6% 9% 37%	1782
November	1st to 10th	Day	8% 13% 5% 9% 6% 4 5% 5% 5% 7% 35%	1565
	11th to 20th	Day	5% 11% 4 7% 5% 3 5% 4 7% 8% 41%	1474
	21st to end	Day	4 9% 8% 7% 5% 3 4 6% 7% 10% 37%	1330
December	1st to 10th	Day	4 11% 4 9% 6% 5% 6% 5% 5% 8% 37%	1330
	11th to 20th	Day	3 11% 6% 10% 9% 4 6% 6% 7% 7% 33%	1682
	21st to end	Day	4 8% 3 7% 5% 4 4 6% 5% 10% 45%	2442
January	1st to 10th	Night	3 10% 6% 10% 9% 5% 7% 6% 7% 8% 29%	4726
	11th to 20th	Night	3 7% 5% 13% 7% 4 6% 8% 6% 8% 34%	4656
	21st to end	Night	4 10% 4 9% 7% 4 5% 4 6% 8% 40%	4862
February	1st to 10th	Night	4 9% 5% 10% 7% 5% 6% 6% 6% 8% 33%	2651
	11th to 20th	Night	4 12% 6% 9% 7% 4 6% 5% 6% 8% 32%	2402
	21st to end	Night	3 8% 6% 10% 10% 5% 5% 5% 5% 6% 36%	1918
March	1st to 10th	Night	2 8% 5% 12% 10% 5% 7% 7% 5% 8% 31%	3736
	11th to 20th	Night	4 7% 4 6% 5% 3 5% 6% 6% 8% 46%	3521
	21st to end	Night	10% 22% 6% 10% 7% 3 5% 4 5% 6% 22%	3779
April	1st to 10th	Night	9% 12% 5% 8% 6% 4 5% 5% 6% 8% 33%	1849
	11th to 20th	Night	10% 12% 5% 8% 7% 4 5% 5% 6% 7% 33%	1691
	21st to end	Night	11% 9% 3 7% 6% 4 6% 4 5% 8% 36%	1665
May	1st to 10th	Night	10% 11% 4 7% 6% 4 4 4 5% 9% 35%	1534
	11th to 20th	Night	10% 7% 3 6% 4 3 5% 5% 6% 10% 41%	1239
	21st to end	Night	19% 6% 3 5% 7% 3 4 6% 6% 7% 34%	1358
June	1st to 10th	Night	14% 6% 3 7% 6% 2 5% 5% 5% 9% 38%	1260
	11th to 20th	Night	18% 6% 3 6% 6% 2 5% 5% 5% 10% 32%	1260
	21st to end	Night	6% 5% 2 4 4 3 4 6% 9% 9% 47%	1260
July	1st to 10th	Night	7% 4 1 4 6% 3 4 5% 5% 9% 51%	1260
	11th to 20th	Night	7% 4 2 4 5% 3 5% 5% 7% 9% 50%	1260
	21st to end	Night	5% 3 1 3 4 3 3 4 6% 8% 60%	1459
August	1st to 10th	Night	8% 4 2 4 5% 4 5% 5% 6% 7% 50%	1432
	11th to 20th	Night	7% 4 1 4 3 3 4 4 6% 10% 54%	1592
	21st to end	Night	9% 4 2 4 3 2 3 3 6% 8% 55%	1782
September	1st to 10th	Night	10% 5% 2 4 5% 3 3 4 6% 8% 51%	1735
	11th to 20th	Night	14% 6% 2 4 3 2 2 4 5% 7% 52%	1980
	21st to end	Night	10% 7% 3 4 4 3 4 5% 6% 8% 48%	1980
October	1st to 10th	Night	10% 8% 3 6% 6% 2 5% 5% 5% 7% 44%	2056
	11th to 20th	Night	8% 7% 3 5% 5% 3 5% 5% 6% 9% 44%	2281
	21st to end	Night	7% 9% 3 6% 6% 3 5% 5% 7% 8% 40%	2574
November	1st to 10th	Night	7% 12% 4 7% 5% 4 6% 5% 5% 8% 36%	2495
	11th to 20th	Night	4 9% 3 8% 6% 4 4 5% 6% 9% 42%	2702
	21st to end	Night	4 9% 5% 7% 6% 3 5% 5% 6% 10% 40%	2850
December	1st to 10th	Night	4 9% 4 8% 7% 4 7% 6% 6% 9% 35%	2850
	11th to 20th	Night	2 8% 5% 10% 8% 4 5% 6% 7% 9% 35%	3510
	21st to end	Night	4 9% 3 7% 6% 4 5% 5% 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% 14% 22% 10% 1	2394
May	1st to 10th	Day	50% 7% 15% 21% 8%	2421
	11th to 20th	Day	43% 7% 15% 23% 11% 1	2658
	21st to end	Day	52% 6% 14% 20% 8% 1	2918
June	1st to 10th	Day	48% 9% 15% 18% 8% 1	2700
	11th to 20th	Day	51% 8% 14% 17% 8% 2	2700
	21st to end	Day	33% 8% 19% 26% 11% 2	2700
July	1st to 10th	Day	32% 8% 18% 26% 13% 2	2626
	11th to 20th	Day	30% 8% 17% 28% 15% 2	2619
	21st to end	Day	23% 7% 16% 33% 18% 3	2695
August	1st to 10th	Day	30% 8% 17% 30% 12% 2	2490
	11th to 20th	Day	28% 7% 22% 28% 11% 3	2308
	21st to end	Day	29% 7% 15% 30% 16% 3	2574
September	1st to 10th	Day	32% 6% 14% 27% 16% 5%	2223
	11th to 20th	Day	37% 6% 13% 28% 14% 2	1980
	21st to end	Day	35% 6% 13% 29% 13% 3	1980
October	1st to 10th	Day	42% 7% 14% 25% 10% 2	1904
	11th to 20th	Day	40% 6% 16% 24% 11% 3	1676
	21st to end	Day	42% 8% 13% 24% 11% 2	1782
November	1st to 10th	Day	49% 6% 12% 19% 12% 2	1565
	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	1665
May	1st to 10th	Night	46% 8% 13% 22% 11%	1534
	11th to 20th	Night	37% 7% 13% 31% 10% 1	1239
	21st to end	Night	48% 7% 16% 20% 7% 1	1358
June	1st to 10th	Night	42% 8% 16% 23% 12%	1260
	11th to 20th	Night	47% 7% 16% 21% 8% 2	1260
	21st to end	Night	28% 8% 22% 27% 13% 2	1260
July	1st to 10th	Night	31% 7% 20% 27% 14% 1	1225
	11th to 20th	Night	29% 9% 18% 27% 13% 4	1218
	21st to end	Night	21% 7% 17% 30% 21% 3	1378
August	1st to 10th	Night	31% 8% 16% 29% 13% 3	1424
	11th to 20th	Night	26% 7% 20% 31% 15% 2	1592
	21st to end	Night	26% 6% 13% 31% 19% 4	1782
September	1st to 10th	Night	31% 6% 16% 27% 16% 4	1735
	11th to 20th	Night	32% 6% 14% 28% 15% 5%	1980
	21st to end	Night	34% 4 16% 27% 14% 5%	1980
October	1st to 10th	Night	40% 6% 13% 24% 16% 1	2056
	11th to 20th	Night	36% 6% 16% 25% 14% 3	2281
	21st to end	Night	40% 7% 15% 25% 12% 1	2574
November	1st to 10th	Night	46% 6% 12% 21% 12% 2	2495
	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	18% 19% 31% 22% 8% 2	437
May	1st to 10th	Day	18% 15% 26% 25% 11% 4	445
	11th to 20th	Day	19% 10% 25% 26% 16% 4	625
	21st to end	Day	20% 9% 23% 29% 16% 3	679
June	1st to 10th	Day	16% 12% 31% 26% 13% 2	630
	11th to 20th	Day	20% 12% 30% 25% 11% 2	630
	21st to end	Day	10% 10% 29% 30% 16% 5%	630
July	1st to 10th	Day	10% 7% 28% 33% 20% 3	621
	11th to 20th	Day	11% 10% 29% 31% 17% 2	618
	21st to end	Day	6% 9% 32% 31% 19% 4	600
August	1st to 10th	Day	10% 8% 32% 33% 13% 4	447
	11th to 20th	Day	9% 7% 31% 32% 16% 6%	437
	21st to end	Day	9% 11% 33% 25% 15% 7%	495
September	1st to 10th	Day	13% 12% 32% 26% 12% 4	450
	11th to 20th	Day	17% 11% 27% 27% 13% 5%	450
	21st to end	Day	15% 18% 26% 26% 11% 3	450
October	1st to 10th	Day	16% 11% 25% 28% 16% 4	374
	11th to 20th	Day	13% 13% 34% 23% 13% 4	270
	21st to end	Day	13% 16% 36% 25% 9% 2	297
November	1st to 10th	Day	21% 11% 33% 23% 8% 3	270
	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% 12% 1	555
May	1st to 10th	Night	16% 11% 26% 32% 15%	478
	11th to 20th	Night	13% 10% 22% 33% 20% 1	354
	21st to end	Night	23% 4 23% 34% 15% 1	389
June	1st to 10th	Night	14% 8% 31% 29% 15% 2	360
	11th to 20th	Night	22% 6% 29% 30% 12% 1	360
	21st to end	Night	9% 6% 20% 42% 22% 2	360
July	1st to 10th	Night	10% 4 20% 41% 25% 1	350
	11th to 20th	Night	10% 3 23% 43% 20% 2	348
	21st to end	Night	7% 4 23% 41% 22% 3	394
August	1st to 10th	Night	11% 4 16% 39% 28% 2	358
	11th to 20th	Night	9% 4 21% 43% 22% 1	524
	21st to end	Night	11% 5% 25% 37% 20% 1	594
September	1st to 10th	Night	12% 5% 25% 36% 19% 3	634
	11th to 20th	Night	17% 5% 23% 35% 18% 3	720
	21st to end	Night	12% 8% 33% 33% 11% 3	720
October	1st to 10th	Night	16% 5% 25% 36% 15% 3	720
	11th to 20th	Night	13% 8% 32% 29% 15% 3	720
	21st to end	Night	12% 9% 33% 34% 11% 1	792
November	1st to 10th	Night	14% 11% 37% 29% 8% 1	830
	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 2024-04-22 07:25:44. Version ac07

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