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 2025-02-06.

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 4 5% 4 6% 7% 42%	112301
	Night	10% 12% 3 7% 4 4 5% 4 5% 6% 39%	114595
Transparency	Day	22% 45% 7% 13% 9% 3	112069
	Night	26% 43% 8% 14% 7% 2	114473
Seeing	Day	14% 18% 32% 25% 9% 2	15137
	Night	15% 9% 29% 32% 14% 1	24027

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	15% 23% 7% 15% 8% 5% 4 3 3 4 14%	3639
	11th to 20th	Day	11% 10% 3 7% 4 5% 6% 4 6% 8% 37%	3616
	21st to end	Day	18% 23% 4 6% 4 3 6% 3 4 4 26%	4004
February	1st to 10th	Day	9% 17% 4 10% 6% 6% 5% 4 6% 7% 28%	1618
	11th to 20th	Day	9% 13% 5% 9% 5% 5% 4 4 5% 8% 32%	1665
	21st to end	Day	7% 13% 4 10% 6% 5% 6% 6% 8% 7% 28%	1570
March	1st to 10th	Day	9% 14% 4 9% 5% 5% 5% 4 7% 8% 31%	3138
	11th to 20th	Day	5% 8% 2 6% 4 4 4 3 5% 7% 51%	3321
	21st to end	Day	11% 12% 3 8% 5% 6% 7% 5% 7% 9% 27%	4128
April	1st to 10th	Day	9% 8% 3 9% 7% 6% 6% 6% 6% 9% 30%	2280
	11th to 20th	Day	7% 9% 2 8% 6% 5% 5% 5% 8% 9% 36%	2258
	21st to end	Day	7% 9% 3 7% 5% 7% 6% 5% 7% 9% 36%	2572
May	1st to 10th	Day	6% 6% 2 6% 5% 4 5% 4 7% 10% 45%	4420
	11th to 20th	Day	6% 5% 2 6% 4 5% 5% 5% 7% 12% 42%	4377
	21st to end	Day	11% 9% 4 8% 6% 7% 6% 6% 7% 8% 29%	4813
June	1st to 10th	Day	12% 7% 2 6% 5% 6% 5% 4 7% 8% 37%	2762
	11th to 20th	Day	10% 7% 3 8% 6% 5% 6% 5% 7% 10% 34%	2912
	21st to end	Day	6% 4 2 6% 5% 5% 5% 4 7% 8% 48%	2972
July	1st to 10th	Day	2 2 1 2 2 2 3 2 4 6% 73%	4553
	11th to 20th	Day	2 2 1 3 2 3 3 3 4 5% 73%	4420
	21st to end	Day	2 2 1 3 2 3 3 3 5% 7% 68%	4790
August	1st to 10th	Day	1 2 1 3 3 3 4 4 6% 7% 66%	4401
	11th to 20th	Day	2 2 1 4 3 4 4 4 6% 8% 61%	4279
	21st to end	Day	5% 3 2 5% 4 4 4 3 5% 8% 56%	4190
September	1st to 10th	Day	4 3 1 4 3 3 4 3 5% 6% 64%	2280
	11th to 20th	Day	7% 4 2 5% 4 5% 4 5% 7% 8% 51%	2254
	21st to end	Day	7% 6% 2 6% 4 4 4 3 6% 8% 51%	2082
October	1st to 10th	Day	6% 4 2 6% 4 4 4 4 5% 8% 54%	3180
	11th to 20th	Day	12% 8% 3 7% 5% 4 5% 4 5% 6% 42%	3076
	21st to end	Day	13% 11% 4 8% 5% 4 4 3 5% 5% 37%	3101
November	1st to 10th	Day	17% 12% 3 8% 5% 5% 5% 4 6% 7% 28%	1704
	11th to 20th	Day	15% 17% 5% 9% 4 4 4 5% 4 5% 28%	1600
	21st to end	Day	13% 20% 7% 11% 5% 3 5% 3 5% 6% 22%	1555
December	1st to 10th	Day	9% 14% 4 8% 6% 7% 6% 4 6% 7% 29%	2290
	11th to 20th	Day	15% 27% 7% 12% 5% 4 4 3 3 4 17%	2642
	21st to end	Day	15% 22% 8% 14% 7% 5% 5% 3 4 4 13%	3839
January	1st to 10th	Night	16% 28% 8% 12% 5% 3 3 2 3 3 16%	6306
	11th to 20th	Night	11% 11% 3 7% 5% 4 5% 4 5% 7% 38%	6282
	21st to end	Night	17% 23% 5% 7% 4 4 5% 3 3 4 25%	6952
February	1st to 10th	Night	11% 18% 5% 10% 5% 5% 5% 4 6% 6% 25%	2669
	11th to 20th	Night	9% 14% 5% 10% 4 4 4 4 6% 7% 33%	2402
	21st to end	Night	8% 14% 4 10% 5% 4 6% 4 7% 6% 30%	1884
March	1st to 10th	Night	6% 12% 4 9% 5% 6% 6% 5% 7% 9% 31%	3736
	11th to 20th	Night	7% 9% 3 5% 3 3 4 4 5% 7% 50%	3654
	21st to end	Night	9% 14% 4 9% 6% 6% 6% 5% 6% 7% 28%	3524
April	1st to 10th	Night	9% 8% 3 6% 4 5% 6% 4 8% 10% 38%	1900
	11th to 20th	Night	6% 7% 3 7% 5% 6% 4 4 6% 9% 42%	1872
	21st to end	Night	5% 8% 2 8% 5% 5% 5% 4 7% 8% 42%	1606
May	1st to 10th	Night	6% 7% 3 6% 4 4 4 4 5% 9% 48%	2540
	11th to 20th	Night	4 4 2 4 3 4 4 4 7% 11% 52%	2516
	21st to end	Night	8% 6% 3 6% 5% 6% 6% 4 8% 10% 39%	2762
June	1st to 10th	Night	9% 7% 3 6% 4 5% 5% 5% 8% 8% 42%	1413
	11th to 20th	Night	10% 6% 2 5% 4 5% 6% 6% 7% 8% 41%	1261
	21st to end	Night	4 2 1 4 4 4 6% 4 6% 9% 55%	1202
July	1st to 10th	Night	2 2 1 2 1 2 3 2 4 5% 78%	2401
	11th to 20th	Night	1 2 1 2 1 2 2 3 4 5% 77%	2540
	21st to end	Night	2 2 1 3 2 3 2 3 5% 6% 71%	2762
August	1st to 10th	Night	2 2 1 4 3 4 5% 4 5% 6% 65%	2529
	11th to 20th	Night	2 2 1 3 3 3 4 4 7% 9% 63%	2547
	21st to end	Night	6% 3 1 4 3 4 3 4 6% 7% 58%	3488
September	1st to 10th	Night	3 4 1 3 3 3 2 3 5% 7% 66%	1900
	11th to 20th	Night	6% 4 1 5% 3 3 3 3 6% 8% 59%	1925
	21st to end	Night	7% 5% 2 6% 4 4 3 4 5% 8% 53%	2095
October	1st to 10th	Night	6% 5% 2 4 4 3 5% 4 6% 7% 54%	3800
	11th to 20th	Night	16% 6% 2 6% 4 4 4 4 5% 7% 42%	3859
	21st to end	Night	14% 8% 3 6% 4 4 4 3 5% 6% 43%	4457
November	1st to 10th	Night	17% 15% 3 6% 5% 3 5% 4 5% 6% 31%	2592
	11th to 20th	Night	17% 16% 3 8% 5% 4 4 4 5% 6% 28%	2800
	21st to end	Night	14% 21% 6% 10% 5% 4 5% 4 4 4 23%	2822
December	1st to 10th	Night	8% 12% 4 10% 6% 7% 8% 4 6% 5% 29%	4890
	11th to 20th	Night	18% 24% 6% 11% 6% 4 4 3 4 4 17%	5550
	21st to end	Night	19% 25% 6% 9% 5% 5% 4 5% 4 4 14%	7157

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	48% 30% 5% 14% 3	3639
	11th to 20th	Day	26% 28% 19% 19% 5% 3	3640
	21st to end	Day	42% 29% 9% 12% 8%	4004
February	1st to 10th	Day	22% 66% 3 5% 3 1	1618
	11th to 20th	Day	21% 65% 4 6% 3	1674
	21st to end	Day	14% 68% 5% 7% 6%	1570
March	1st to 10th	Day	30% 46% 4 10% 10% 1	3138
	11th to 20th	Day	13% 44% 13% 27% 3	3321
	21st to end	Day	31% 47% 7% 8% 7%	4128
April	1st to 10th	Day	17% 67% 7% 7% 3	2280
	11th to 20th	Day	14% 68% 4 10% 3 1	2258
	21st to end	Day	16% 67% 5% 6% 6%	2572
May	1st to 10th	Day	17% 47% 6% 16% 14% 1	4420
	11th to 20th	Day	18% 44% 11% 19% 8%	4380
	21st to end	Day	28% 47% 9% 13% 3	4814
June	1st to 10th	Day	14% 67% 5% 9% 4 1	2762
	11th to 20th	Day	13% 68% 5% 9% 4	2912
	21st to end	Day	12% 65% 4 11% 7% 1	2972
July	1st to 10th	Day	6% 36% 3 10% 24% 20%	4484
	11th to 20th	Day	7% 36% 2 6% 23% 26%	4345
	21st to end	Day	12% 35% 6% 17% 20% 10%	4639
August	1st to 10th	Day	10% 37% 2 18% 26% 7%	4384
	11th to 20th	Day	15% 38% 13% 27% 6% 2	4321
	21st to end	Day	20% 37% 10% 17% 13% 3	4189
September	1st to 10th	Day	11% 61% 6% 12% 8% 1	2280
	11th to 20th	Day	13% 63% 5% 10% 7% 1	2254
	21st to end	Day	14% 62% 7% 10% 6% 1	2082
October	1st to 10th	Day	21% 37% 12% 26% 4	3180
	11th to 20th	Day	33% 38% 4 19% 5%	3076
	21st to end	Day	34% 36% 7% 15% 8%	3101
November	1st to 10th	Day	24% 58% 8% 8% 2	1704
	11th to 20th	Day	25% 58% 6% 6% 3 1	1600
	21st to end	Day	26% 58% 6% 6% 4 1	1555
December	1st to 10th	Day	30% 37% 19% 12% 2	2290
	11th to 20th	Day	49% 33% 7% 7% 4	2644
	21st to end	Day	54% 30% 7% 7% 2	3839
January	1st to 10th	Night	53% 28% 6% 12% 2	6306
	11th to 20th	Night	27% 29% 14% 17% 10% 4	6320
	21st to end	Night	44% 29% 9% 12% 6%	6952
February	1st to 10th	Night	24% 64% 3 5% 3 1	2669
	11th to 20th	Night	20% 65% 4 6% 3 1	2404
	21st to end	Night	15% 67% 5% 9% 5%	1884
March	1st to 10th	Night	23% 49% 5% 12% 11%	3736
	11th to 20th	Night	13% 42% 12% 26% 6%	3655
	21st to end	Night	32% 47% 7% 10% 4	3524
April	1st to 10th	Night	15% 67% 6% 8% 3 1	1900
	11th to 20th	Night	15% 67% 4 8% 5% 1	1872
	21st to end	Night	13% 67% 4 9% 7%	1606
May	1st to 10th	Night	19% 43% 6% 15% 16%	2540
	11th to 20th	Night	13% 43% 10% 24% 7% 3	2516
	21st to end	Night	18% 46% 12% 19% 4	2762
June	1st to 10th	Night	12% 66% 5% 12% 5%	1413
	11th to 20th	Night	14% 66% 4 9% 6% 1	1261
	21st to end	Night	11% 64% 4 14% 7% 1	1202
July	1st to 10th	Night	5% 36% 2 11% 27% 19%	2361
	11th to 20th	Night	6% 36% 3 6% 22% 26%	2492
	21st to end	Night	13% 35% 4 19% 20% 10%	2674
August	1st to 10th	Night	13% 37% 2 17% 28% 4	2521
	11th to 20th	Night	14% 37% 13% 25% 9% 1	2571
	21st to end	Night	21% 36% 10% 21% 11% 1	3488
September	1st to 10th	Night	9% 61% 6% 13% 9% 1	1900
	11th to 20th	Night	12% 62% 5% 12% 8% 1	1925
	21st to end	Night	15% 61% 6% 12% 5%	2095
October	1st to 10th	Night	21% 37% 11% 22% 8%	3800
	11th to 20th	Night	30% 37% 6% 17% 9%	3859
	21st to end	Night	29% 37% 8% 21% 5%	4457
November	1st to 10th	Night	23% 59% 8% 8% 3	2592
	11th to 20th	Night	23% 59% 6% 6% 4 2	2800
	21st to end	Night	25% 58% 6% 5% 4 1	2822
December	1st to 10th	Night	24% 38% 15% 20% 2	4890
	11th to 20th	Night	50% 34% 8% 6% 2	5547
	21st to end	Night	49% 28% 9% 10% 4	7157

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	20% 15% 28% 25% 10% 3	200
	11th to 20th	Day	22% 14% 28% 22% 12% 3	200
	21st to end	Day	26% 13% 30% 23% 5% 3	220
February	1st to 10th	Day	15% 21% 45% 17% 2	248
	11th to 20th	Day	19% 17% 38% 20% 6%	365
	21st to end	Day	11% 21% 38% 24% 6% 1	382
March	1st to 10th	Day	20% 25% 29% 20% 5% 1	460
	11th to 20th	Day	16% 23% 29% 18% 12% 2	460
	21st to end	Day	20% 24% 29% 19% 7% 2	506
April	1st to 10th	Day	22% 23% 30% 18% 5% 2	460
	11th to 20th	Day	17% 27% 27% 19% 6% 3	452
	21st to end	Day	14% 26% 28% 22% 7% 3	460
May	1st to 10th	Day	12% 23% 32% 23% 8% 2	463
	11th to 20th	Day	16% 15% 33% 22% 11% 3	488
	21st to end	Day	15% 16% 31% 24% 10% 3	529
June	1st to 10th	Day	17% 18% 34% 24% 5% 1	592
	11th to 20th	Day	12% 20% 32% 26% 9% 1	742
	21st to end	Day	6% 14% 38% 28% 12% 1	802
July	1st to 10th	Day	7% 14% 34% 35% 9% 1	567
	11th to 20th	Day	7% 18% 33% 30% 11% 2	484
	21st to end	Day	4 13% 35% 33% 12% 3	531
August	1st to 10th	Day	3 12% 32% 35% 13% 5%	487
	11th to 20th	Day	5% 12% 29% 33% 17% 4	477
	21st to end	Day	8% 17% 31% 30% 8% 6%	539
September	1st to 10th	Day	9% 17% 32% 24% 12% 6%	490
	11th to 20th	Day	12% 17% 31% 26% 10% 4	490
	21st to end	Day	16% 19% 31% 22% 10% 2	490
October	1st to 10th	Day	13% 20% 32% 22% 11% 2	490
	11th to 20th	Day	16% 21% 23% 27% 10% 3	443
	21st to end	Day	22% 20% 28% 22% 7% 1	330
November	1st to 10th	Day	24% 15% 30% 24% 7%	270
	11th to 20th	Day	25% 19% 32% 17% 6% 2	200
	21st to end	Day	23% 18% 27% 20% 11% 3	200
December	1st to 10th	Day	23% 10% 24% 27% 14% 4	200
	11th to 20th	Day	21% 17% 30% 23% 8% 2	200
	21st to end	Day	20% 15% 30% 26% 7% 2	220
January	1st to 10th	Night	25% 10% 28% 27% 9% 2	800
	11th to 20th	Night	21% 8% 30% 29% 10% 2	800
	21st to end	Night	20% 8% 28% 30% 13% 1	880
February	1st to 10th	Night	18% 9% 33% 29% 9% 1	780
	11th to 20th	Night	14% 7% 34% 31% 13% 1	744
	21st to end	Night	13% 11% 30% 32% 14% 1	628
March	1st to 10th	Night	14% 9% 32% 29% 14% 1	760
	11th to 20th	Night	13% 10% 32% 29% 15% 1	760
	21st to end	Night	14% 11% 35% 30% 10% 1	836
April	1st to 10th	Night	14% 10% 29% 33% 15% 1	760
	11th to 20th	Night	9% 10% 35% 31% 13% 2	744
	21st to end	Night	9% 12% 38% 30% 10% 1	466
May	1st to 10th	Night	9% 9% 36% 34% 11% 1	380
	11th to 20th	Night	10% 6% 28% 34% 20% 2	374
	21st to end	Night	10% 9% 28% 38% 15%	411
June	1st to 10th	Night	12% 10% 31% 34% 14%	380
	11th to 20th	Night	13% 6% 36% 33% 11%	380
	21st to end	Night	6% 8% 32% 38% 16% 1	380
July	1st to 10th	Night	5% 4 30% 41% 19% 1	370
	11th to 20th	Night	2 7% 36% 38% 18%	368
	21st to end	Night	4 5% 27% 44% 19% 1	416
August	1st to 10th	Night	4 5% 20% 43% 26% 1	378
	11th to 20th	Night	3 3 24% 42% 26% 3	400
	21st to end	Night	6% 6% 26% 38% 22% 2	826
September	1st to 10th	Night	5% 7% 24% 36% 25% 2	760
	11th to 20th	Night	9% 6% 21% 32% 29% 3	760
	21st to end	Night	11% 8% 26% 34% 18% 3	760
October	1st to 10th	Night	14% 8% 27% 29% 19% 2	760
	11th to 20th	Night	16% 8% 27% 33% 14% 2	760
	21st to end	Night	21% 8% 26% 31% 11% 3	836
November	1st to 10th	Night	23% 9% 29% 32% 7%	780
	11th to 20th	Night	25% 10% 29% 22% 13% 2	800
	21st to end	Night	22% 10% 27% 27% 12% 2	822
December	1st to 10th	Night	17% 8% 30% 31% 12% 1	1000
	11th to 20th	Night	24% 11% 30% 27% 7% 1	1000
	21st to end	Night	25% 11% 30% 29% 6%	968

Page generated at 2025-02-03 00:05:52. Version ac07

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