Osoyoos
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Osoyoos clear sky chart from 2005-11-06 to 2026-06-01.

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 7% 4 5% 5% 4 6% 7% 43%	136068
	Night	10% 12% 3 7% 4 4 5% 4 5% 6% 39%	135773
Transparency	Day	25% 38% 8% 17% 9% 3	135795
	Night	29% 37% 8% 16% 8% 2	135624
Seeing	Day	14% 18% 32% 25% 9% 2	16864
	Night	15% 9% 30% 32% 14% 1	25655

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	16% 23% 6% 14% 7% 5% 4 3 3 4 14%	4723
	11th to 20th	Day	9% 8% 3 6% 5% 5% 5% 4 5% 7% 43%	4716
	21st to end	Day	17% 20% 4 6% 4 4 6% 3 5% 5% 27%	5186
February	1st to 10th	Day	9% 16% 4 9% 6% 6% 5% 3 6% 7% 28%	1745
	11th to 20th	Day	9% 13% 5% 10% 5% 5% 4 4 5% 8% 32%	1845
	21st to end	Day	8% 13% 4 10% 6% 5% 6% 6% 8% 7% 28%	1730
March	1st to 10th	Day	6% 10% 3 7% 4 5% 6% 6% 8% 9% 35%	4618
	11th to 20th	Day	6% 10% 3 8% 5% 5% 5% 4 6% 7% 42%	4857
	21st to end	Day	11% 11% 3 7% 5% 6% 7% 5% 7% 9% 27%	6050
April	1st to 10th	Day	8% 8% 3 9% 7% 6% 6% 6% 6% 9% 32%	2520
	11th to 20th	Day	6% 8% 2 8% 5% 5% 5% 5% 8% 9% 38%	2499
	21st to end	Day	6% 8% 3 6% 5% 6% 5% 5% 7% 9% 39%	2843
May	1st to 10th	Day	6% 6% 2 6% 5% 5% 4 3 6% 8% 50%	6460
	11th to 20th	Day	7% 7% 3 7% 5% 5% 6% 5% 7% 11% 36%	6417
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 5% 7% 10% 38%	7057
June	1st to 10th	Day	11% 7% 2 6% 5% 5% 5% 4 7% 8% 39%	2909
	11th to 20th	Day	9% 6% 2 8% 6% 5% 6% 5% 7% 10% 35%	3066
	21st to end	Day	6% 4 2 6% 5% 5% 5% 4 7% 8% 48%	3128
July	1st to 10th	Day	2 2 1 2 2 2 3 2 4 6% 72%	6509
	11th to 20th	Day	2 2 1 3 2 2 3 2 4 5% 74%	6320
	21st to end	Day	3 3 1 3 2 3 4 3 5% 8% 64%	6874
August	1st to 10th	Day	1 2 1 3 3 3 4 4 6% 8% 65%	4541
	11th to 20th	Day	2 2 1 4 3 4 4 4 6% 8% 61%	4417
	21st to end	Day	5% 3 2 5% 3 4 4 3 5% 8% 56%	4322
September	1st to 10th	Day	4 3 1 4 3 3 4 3 5% 6% 64%	2400
	11th to 20th	Day	6% 4 2 4 3 5% 4 4 6% 8% 52%	2372
	21st to end	Day	7% 5% 2 6% 3 4 4 3 5% 7% 52%	2191
October	1st to 10th	Day	6% 4 2 6% 4 4 4 4 5% 8% 54%	3280
	11th to 20th	Day	12% 8% 3 7% 5% 4 5% 3 5% 6% 42%	3173
	21st to end	Day	13% 11% 4 8% 5% 5% 5% 3 5% 5% 37%	3200
November	1st to 10th	Day	17% 12% 3 8% 5% 5% 5% 4 6% 6% 29%	1791
	11th to 20th	Day	15% 17% 5% 9% 5% 4 4 5% 4 5% 27%	1680
	21st to end	Day	13% 20% 7% 11% 5% 3 5% 3 5% 6% 22%	1633
December	1st to 10th	Day	9% 14% 4 9% 6% 7% 6% 4 5% 7% 28%	2360
	11th to 20th	Day	15% 27% 6% 12% 5% 4 4 3 3 4 17%	2712
	21st to end	Day	15% 22% 8% 14% 7% 5% 5% 3 4 4 13%	3924
January	1st to 10th	Night	17% 27% 7% 12% 5% 3 3 2 4 4 16%	8172
	11th to 20th	Night	10% 9% 2 8% 5% 5% 5% 4 5% 7% 40%	8182
	21st to end	Night	16% 20% 5% 7% 5% 4 5% 3 4 4 28%	8994
February	1st to 10th	Night	11% 18% 4 10% 6% 5% 5% 4 6% 6% 25%	2872
	11th to 20th	Night	9% 14% 5% 10% 4 4 4 4 5% 7% 33%	2662
	21st to end	Night	9% 14% 5% 10% 5% 4 6% 4 7% 6% 30%	2076
March	1st to 10th	Night	5% 9% 3 7% 5% 6% 6% 5% 7% 9% 37%	5496
	11th to 20th	Night	8% 11% 3 6% 4 4 4 4 5% 7% 43%	5345
	21st to end	Night	11% 13% 4 10% 7% 7% 6% 5% 6% 7% 25%	5166
April	1st to 10th	Night	9% 8% 2 6% 4 5% 6% 4 7% 10% 39%	2100
	11th to 20th	Night	5% 7% 2 7% 5% 5% 5% 4 7% 9% 43%	2071
	21st to end	Night	5% 7% 2 7% 5% 4 5% 4 7% 9% 43%	1775
May	1st to 10th	Night	5% 5% 2 5% 3 5% 4 4 5% 8% 53%	3720
	11th to 20th	Night	7% 5% 2 6% 4 5% 5% 4 7% 9% 46%	3696
	21st to end	Night	8% 4 2 5% 4 5% 5% 4 7% 10% 46%	4060
June	1st to 10th	Night	8% 6% 3 6% 4 5% 5% 5% 7% 8% 43%	1487
	11th to 20th	Night	9% 6% 2 5% 4 5% 6% 6% 7% 8% 42%	1327
	21st to end	Night	5% 3 1 4 4 4 6% 4 5% 9% 55%	1266
July	1st to 10th	Night	1 2 1 2 1 2 3 2 4 6% 75%	3445
	11th to 20th	Night	1 2 1 2 1 2 2 3 4 6% 76%	3640
	21st to end	Night	3 2 1 3 2 3 3 3 5% 7% 67%	3969
August	1st to 10th	Night	2 2 1 4 4 4 5% 4 5% 6% 64%	2609
	11th to 20th	Night	2 2 1 3 3 4 4 4 7% 9% 62%	2628
	21st to end	Night	6% 3 2 4 3 4 3 4 6% 7% 58%	3598
September	1st to 10th	Night	3 4 1 3 3 3 3 3 5% 7% 66%	2000
	11th to 20th	Night	6% 4 1 5% 3 3 3 3 5% 8% 59%	2027
	21st to end	Night	7% 4 2 6% 4 4 3 4 5% 8% 53%	2205
October	1st to 10th	Night	6% 5% 2 4 4 3 5% 4 6% 7% 54%	3920
	11th to 20th	Night	16% 6% 2 6% 4 4 4 4 5% 7% 42%	3982
	21st to end	Night	14% 8% 3 6% 4 4 4 3 5% 6% 43%	4600
November	1st to 10th	Night	17% 15% 3 6% 5% 3 5% 4 5% 6% 31%	2725
	11th to 20th	Night	18% 16% 3 8% 4 4 4 4 5% 6% 27%	2940
	21st to end	Night	14% 21% 6% 10% 6% 4 5% 4 4 4 23%	2963
December	1st to 10th	Night	8% 13% 4 10% 6% 7% 8% 4 6% 5% 28%	5040
	11th to 20th	Night	18% 24% 6% 11% 6% 4 4 3 4 4 17%	5700
	21st to end	Night	19% 25% 5% 9% 5% 5% 4 5% 4 4 14%	7315

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	53% 24% 6% 13% 3	4723
	11th to 20th	Day	25% 22% 17% 26% 8% 2	4740
	21st to end	Day	45% 23% 10% 14% 8%	5187
February	1st to 10th	Day	24% 61% 3 6% 6% 1	1745
	11th to 20th	Day	25% 59% 5% 7% 4	1854
	21st to end	Day	19% 62% 7% 7% 6%	1730
March	1st to 10th	Day	33% 32% 6% 14% 14% 1	4618
	11th to 20th	Day	29% 31% 10% 25% 5%	4857
	21st to end	Day	40% 33% 8% 12% 7%	6050
April	1st to 10th	Day	18% 61% 9% 9% 3	2520
	11th to 20th	Day	16% 61% 6% 12% 4 1	2499
	21st to end	Day	16% 61% 6% 9% 7% 1	2843
May	1st to 10th	Day	22% 32% 4 23% 17% 2	6460
	11th to 20th	Day	32% 31% 11% 19% 7%	6420
	21st to end	Day	27% 32% 13% 22% 6%	7058
June	1st to 10th	Day	14% 64% 5% 11% 6% 1	2909
	11th to 20th	Day	14% 65% 5% 10% 6%	3066
	21st to end	Day	13% 62% 5% 13% 7%	3128
July	1st to 10th	Day	9% 26% 7% 18% 24% 16%	6440
	11th to 20th	Day	9% 25% 5% 23% 19% 18%	6245
	21st to end	Day	16% 25% 8% 26% 18% 7%	6681
August	1st to 10th	Day	11% 36% 3 19% 25% 7%	4524
	11th to 20th	Day	16% 36% 13% 27% 6% 2	4459
	21st to end	Day	20% 36% 10% 18% 13% 3	4321
September	1st to 10th	Day	11% 58% 7% 13% 10% 2	2400
	11th to 20th	Day	14% 60% 5% 11% 8% 1	2372
	21st to end	Day	15% 59% 8% 12% 6% 1	2191
October	1st to 10th	Day	21% 36% 13% 26% 4	3280
	11th to 20th	Day	33% 37% 4 20% 6%	3173
	21st to end	Day	35% 36% 7% 15% 8%	3200
November	1st to 10th	Day	24% 55% 8% 9% 3	1791
	11th to 20th	Day	27% 56% 6% 6% 3 1	1680
	21st to end	Day	28% 55% 6% 6% 4 1	1633
December	1st to 10th	Day	31% 37% 19% 12% 2	2360
	11th to 20th	Day	50% 32% 7% 7% 4	2714
	21st to end	Day	54% 29% 7% 7% 2	3924
January	1st to 10th	Night	57% 22% 8% 11% 2	8172
	11th to 20th	Night	27% 23% 12% 24% 10% 3	8220
	21st to end	Night	44% 23% 10% 15% 8%	8994
February	1st to 10th	Night	26% 60% 3 6% 4 1	2872
	11th to 20th	Night	24% 59% 5% 8% 4 1	2664
	21st to end	Night	19% 61% 6% 9% 5%	2076
March	1st to 10th	Night	27% 34% 6% 20% 12% 1	5496
	11th to 20th	Night	28% 29% 11% 22% 10%	5346
	21st to end	Night	45% 33% 6% 11% 5%	5166
April	1st to 10th	Night	17% 60% 7% 11% 3 1	2100
	11th to 20th	Night	16% 61% 6% 11% 5% 1	2071
	21st to end	Night	14% 61% 4 13% 8% 1	1775
May	1st to 10th	Night	22% 29% 5% 23% 21% 1	3717
	11th to 20th	Night	27% 30% 10% 26% 5% 2	3696
	21st to end	Night	20% 32% 14% 28% 5%	4060
June	1st to 10th	Night	12% 63% 5% 13% 7%	1487
	11th to 20th	Night	15% 63% 4 9% 8% 1	1327
	21st to end	Night	12% 61% 5% 15% 6% 1	1266
July	1st to 10th	Night	10% 25% 8% 17% 26% 15%	3405
	11th to 20th	Night	9% 25% 8% 20% 19% 18%	3592
	21st to end	Night	17% 25% 4 30% 17% 7%	3857
August	1st to 10th	Night	14% 36% 2 18% 27% 4	2601
	11th to 20th	Night	15% 36% 13% 25% 10% 1	2652
	21st to end	Night	21% 35% 10% 21% 11% 2	3598
September	1st to 10th	Night	10% 58% 7% 13% 11% 1	2000
	11th to 20th	Night	13% 59% 5% 14% 9%	2027
	21st to end	Night	16% 58% 6% 14% 5%	2205
October	1st to 10th	Night	21% 36% 11% 23% 8%	3920
	11th to 20th	Night	30% 36% 7% 18% 9%	3982
	21st to end	Night	30% 36% 9% 21% 5%	4600
November	1st to 10th	Night	25% 56% 8% 8% 3	2725
	11th to 20th	Night	25% 57% 7% 6% 4 2	2940
	21st to end	Night	27% 56% 6% 6% 4 1	2963
December	1st to 10th	Night	26% 37% 15% 20% 2	5040
	11th to 20th	Night	50% 33% 7% 7% 2	5697
	21st to end	Night	49% 28% 9% 10% 4	7315

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	21% 14% 29% 24% 10% 2	220
	11th to 20th	Day	20% 14% 29% 23% 11% 3	220
	21st to end	Day	26% 12% 31% 23% 5% 2	242
February	1st to 10th	Day	17% 18% 42% 19% 4	285
	11th to 20th	Day	19% 16% 38% 20% 7% 1	425
	21st to end	Day	13% 20% 38% 23% 6%	446
March	1st to 10th	Day	20% 22% 29% 22% 6% 1	540
	11th to 20th	Day	18% 23% 30% 18% 11% 1	540
	21st to end	Day	20% 21% 32% 20% 6% 2	594
April	1st to 10th	Day	20% 21% 29% 20% 8% 2	540
	11th to 20th	Day	17% 26% 27% 20% 7% 3	532
	21st to end	Day	14% 24% 28% 23% 9% 3	540
May	1st to 10th	Day	12% 22% 33% 23% 8% 2	543
	11th to 20th	Day	16% 15% 34% 22% 10% 3	568
	21st to end	Day	15% 17% 31% 24% 11% 2	617
June	1st to 10th	Day	17% 18% 35% 24% 6% 1	639
	11th to 20th	Day	12% 20% 32% 27% 8% 1	796
	21st to end	Day	7% 14% 37% 28% 13% 1	858
July	1st to 10th	Day	6% 15% 35% 34% 9% 1	611
	11th to 20th	Day	7% 17% 35% 29% 10% 2	524
	21st to end	Day	4 13% 36% 32% 13% 3	575
August	1st to 10th	Day	3 12% 32% 35% 14% 4	527
	11th to 20th	Day	5% 13% 29% 33% 17% 4	517
	21st to end	Day	8% 16% 30% 30% 9% 6%	583
September	1st to 10th	Day	8% 16% 31% 24% 14% 7%	530
	11th to 20th	Day	12% 16% 31% 26% 11% 5%	530
	21st to end	Day	15% 19% 32% 22% 9% 2	530
October	1st to 10th	Day	12% 19% 34% 21% 11% 2	530
	11th to 20th	Day	17% 20% 24% 26% 10% 3	480
	21st to end	Day	22% 19% 29% 22% 7% 1	363
November	1st to 10th	Day	24% 15% 32% 23% 7%	297
	11th to 20th	Day	25% 18% 32% 17% 6% 2	220
	21st to end	Day	25% 18% 28% 18% 10% 2	220
December	1st to 10th	Day	24% 10% 25% 25% 13% 3	220
	11th to 20th	Day	21% 16% 31% 22% 7% 2	220
	21st to end	Day	20% 14% 31% 26% 7% 2	242
January	1st to 10th	Night	26% 10% 28% 26% 8% 2	840
	11th to 20th	Night	21% 8% 30% 29% 11% 1	840
	21st to end	Night	20% 8% 28% 31% 13% 1	924
February	1st to 10th	Night	20% 9% 32% 28% 10% 1	840
	11th to 20th	Night	14% 8% 34% 31% 12% 1	824
	21st to end	Night	14% 10% 31% 30% 13% 1	692
March	1st to 10th	Night	13% 9% 32% 30% 14% 1	840
	11th to 20th	Night	14% 10% 33% 29% 14% 1	840
	21st to end	Night	15% 10% 35% 29% 10% 1	924
April	1st to 10th	Night	13% 10% 28% 34% 15%	840
	11th to 20th	Night	9% 10% 36% 31% 13% 2	823
	21st to end	Night	9% 12% 37% 30% 10% 1	515
May	1st to 10th	Night	9% 9% 37% 35% 10% 1	420
	11th to 20th	Night	10% 6% 30% 33% 19% 2	414
	21st to end	Night	10% 9% 28% 38% 14%	455
June	1st to 10th	Night	11% 10% 32% 34% 13%	400
	11th to 20th	Night	13% 7% 36% 34% 11%	400
	21st to end	Night	6% 9% 32% 37% 17% 1	400
July	1st to 10th	Night	5% 5% 30% 40% 18% 1	390
	11th to 20th	Night	2 7% 36% 37% 18%	388
	21st to end	Night	4 5% 26% 44% 20% 1	438
August	1st to 10th	Night	4 5% 20% 44% 26% 1	398
	11th to 20th	Night	3 3 25% 42% 25% 3	421
	21st to end	Night	6% 6% 26% 38% 23% 2	870
September	1st to 10th	Night	5% 7% 23% 36% 26% 2	800
	11th to 20th	Night	8% 6% 21% 34% 28% 3	800
	21st to end	Night	11% 7% 27% 35% 18% 3	800
October	1st to 10th	Night	14% 8% 29% 29% 19% 2	800
	11th to 20th	Night	16% 8% 27% 33% 14% 2	800
	21st to end	Night	21% 9% 26% 32% 10% 2	880
November	1st to 10th	Night	24% 9% 30% 31% 6%	820
	11th to 20th	Night	26% 9% 28% 22% 13% 2	840
	21st to end	Night	23% 10% 27% 27% 11% 2	863
December	1st to 10th	Night	18% 8% 30% 31% 12% 1	1050
	11th to 20th	Night	24% 11% 31% 27% 6%	1050
	21st to end	Night	24% 11% 30% 29% 6%	1016

Page generated at 2026-05-28 22:53:25. Version ac07

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