McBride
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McBride 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	9% 13% 5% 11% 7% 7% 6% 5% 6% 7% 25%	111417
	Night	7% 13% 5% 12% 7% 7% 6% 5% 7% 7% 23%	115463
Transparency	Day	55% 9% 16% 14% 5% 1	111153
	Night	55% 10% 16% 13% 4	115373
Seeing	Day	20% 15% 30% 24% 10% 1	16479
	Night	19% 11% 32% 26% 11% 1	24790

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	3 15% 5% 17% 12% 10% 8% 5% 6% 6% 14%	2742
	11th to 20th	Day	3 10% 7% 14% 7% 7% 8% 5% 6% 8% 25%	3159
	21st to end	Day	5% 13% 6% 12% 9% 7% 7% 6% 6% 9% 21%	3792
February	1st to 10th	Day	6% 19% 8% 14% 7% 7% 6% 5% 6% 6% 18%	1560
	11th to 20th	Day	4 20% 8% 16% 8% 6% 6% 4 6% 4 18%	1631
	21st to end	Day	2 13% 6% 19% 11% 7% 7% 4 5% 5% 21%	1475
March	1st to 10th	Day	1 9% 5% 13% 11% 11% 10% 7% 7% 7% 19%	3138
	11th to 20th	Day	3 14% 6% 13% 8% 7% 6% 5% 6% 8% 24%	3352
	21st to end	Day	2 16% 6% 15% 9% 7% 8% 5% 6% 6% 21%	4098
April	1st to 10th	Day	4 19% 8% 18% 9% 8% 6% 4 7% 6% 12%	2280
	11th to 20th	Day	4 18% 6% 13% 9% 7% 6% 4 6% 7% 20%	2367
	21st to end	Day	6% 18% 6% 14% 7% 6% 6% 4 6% 7% 20%	2660
May	1st to 10th	Day	9% 14% 5% 12% 7% 6% 5% 4 5% 7% 25%	4420
	11th to 20th	Day	10% 15% 5% 12% 8% 6% 6% 5% 6% 7% 20%	4440
	21st to end	Day	15% 19% 6% 12% 7% 6% 5% 4 5% 5% 15%	5439
June	1st to 10th	Day	16% 12% 4 10% 7% 6% 6% 5% 6% 6% 22%	3040
	11th to 20th	Day	21% 15% 5% 11% 7% 7% 6% 4 6% 5% 14%	3040
	21st to end	Day	16% 12% 4 11% 7% 6% 6% 4 6% 7% 23%	3040
July	1st to 10th	Day	13% 6% 2 7% 5% 5% 5% 4 6% 6% 41%	5060
	11th to 20th	Day	8% 6% 2 6% 5% 5% 5% 5% 6% 7% 46%	4946
	21st to end	Day	14% 7% 2 9% 7% 6% 6% 5% 6% 8% 30%	4999
August	1st to 10th	Day	8% 6% 2 6% 5% 5% 5% 4 6% 7% 45%	4401
	11th to 20th	Day	11% 7% 2 8% 6% 5% 6% 5% 7% 7% 35%	4330
	21st to end	Day	17% 8% 3 8% 6% 5% 5% 4 6% 7% 31%	4463
September	1st to 10th	Day	14% 12% 4 10% 7% 5% 4 3 5% 6% 30%	2280
	11th to 20th	Day	12% 11% 4 10% 6% 6% 5% 3 5% 8% 30%	2280
	21st to end	Day	17% 14% 3 11% 6% 7% 5% 4 5% 6% 23%	2034
October	1st to 10th	Day	15% 13% 3 9% 5% 6% 6% 5% 6% 8% 23%	3180
	11th to 20th	Day	14% 14% 4 10% 6% 6% 5% 4 6% 8% 22%	3012
	21st to end	Day	6% 14% 5% 10% 6% 7% 7% 6% 7% 6% 27%	3048
November	1st to 10th	Day	9% 19% 6% 14% 8% 7% 6% 4 7% 5% 15%	1568
	11th to 20th	Day	6% 15% 7% 15% 9% 8% 8% 6% 6% 6% 15%	1480
	21st to end	Day	5% 20% 7% 14% 9% 8% 6% 5% 6% 6% 14%	1400
December	1st to 10th	Day	5% 12% 5% 13% 9% 9% 9% 7% 7% 8% 18%	2009
	11th to 20th	Day	2 16% 6% 12% 8% 8% 9% 5% 7% 7% 19%	2262
	21st to end	Day	2 14% 5% 13% 7% 8% 7% 5% 9% 8% 22%	2992
January	1st to 10th	Night	3 14% 6% 17% 10% 9% 9% 6% 7% 6% 12%	7226
	11th to 20th	Night	4 15% 6% 13% 8% 8% 8% 6% 7% 6% 20%	6760
	21st to end	Night	4 18% 7% 15% 9% 7% 6% 4 6% 5% 19%	7164
February	1st to 10th	Night	6% 20% 8% 13% 10% 6% 6% 4 6% 7% 15%	2730
	11th to 20th	Night	5% 19% 9% 15% 8% 6% 5% 5% 6% 7% 16%	2435
	21st to end	Night	2 15% 7% 17% 9% 6% 6% 4 6% 7% 22%	1979
March	1st to 10th	Night	1 9% 5% 14% 12% 9% 8% 6% 9% 7% 19%	3736
	11th to 20th	Night	5% 15% 5% 11% 7% 7% 8% 6% 8% 9% 18%	3627
	21st to end	Night	2 15% 6% 11% 6% 6% 6% 5% 7% 8% 28%	3554
April	1st to 10th	Night	4 16% 6% 13% 8% 7% 6% 6% 6% 7% 21%	1900
	11th to 20th	Night	3 13% 6% 10% 8% 7% 7% 6% 7% 9% 25%	1758
	21st to end	Night	8% 16% 5% 11% 6% 7% 6% 5% 5% 6% 26%	1520
May	1st to 10th	Night	8% 12% 5% 11% 6% 6% 6% 4 7% 8% 27%	2540
	11th to 20th	Night	12% 13% 4 10% 7% 5% 6% 4 7% 7% 26%	2453
	21st to end	Night	16% 18% 5% 10% 6% 5% 4 4 5% 6% 21%	2133
June	1st to 10th	Night	14% 11% 4 9% 6% 6% 6% 5% 6% 6% 28%	1140
	11th to 20th	Night	19% 12% 4 8% 6% 5% 6% 4 6% 8% 20%	1140
	21st to end	Night	12% 7% 3 9% 5% 6% 6% 4 8% 9% 30%	1140
July	1st to 10th	Night	13% 6% 2 5% 5% 4 4 3 5% 6% 46%	1900
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 4 4 7% 53%	2012
	21st to end	Night	14% 6% 2 6% 5% 6% 6% 4 6% 7% 38%	2539
August	1st to 10th	Night	8% 5% 2 6% 5% 4 4 4 6% 8% 49%	2529
	11th to 20th	Night	10% 6% 3 7% 5% 5% 5% 4 6% 9% 41%	2497
	21st to end	Night	18% 8% 3 7% 5% 4 5% 4 6% 7% 32%	3204
September	1st to 10th	Night	16% 9% 4 9% 5% 5% 5% 4 5% 7% 33%	1900
	11th to 20th	Night	13% 10% 3 8% 5% 4 4 3 5% 6% 37%	1900
	21st to end	Night	19% 12% 4 8% 5% 4 4 4 5% 6% 28%	2142
October	1st to 10th	Night	12% 13% 3 9% 5% 6% 7% 5% 7% 9% 25%	3800
	11th to 20th	Night	12% 12% 3 8% 6% 6% 6% 5% 7% 11% 24%	3921
	21st to end	Night	7% 15% 5% 11% 7% 7% 6% 5% 6% 7% 24%	4507
November	1st to 10th	Night	11% 18% 6% 13% 9% 8% 7% 5% 6% 5% 12%	2730
	11th to 20th	Night	7% 17% 7% 14% 10% 8% 7% 5% 6% 6% 14%	2899
	21st to end	Night	6% 20% 7% 14% 9% 7% 7% 5% 7% 6% 12%	3000
December	1st to 10th	Night	6% 13% 5% 13% 8% 8% 7% 6% 7% 9% 18%	5154
	11th to 20th	Night	3 16% 7% 14% 10% 7% 7% 6% 7% 7% 16%	5930
	21st to end	Night	2 13% 6% 14% 7% 7% 7% 6% 8% 9% 21%	7964

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	65% 12% 14% 6% 3	2742
	11th to 20th	Day	55% 12% 11% 10% 8% 5%	3180
	21st to end	Day	58% 14% 17% 8% 2	3792
February	1st to 10th	Day	64% 7% 10% 8% 10% 1	1560
	11th to 20th	Day	66% 6% 12% 10% 5% 1	1640
	21st to end	Day	62% 7% 11% 13% 5% 3	1475
March	1st to 10th	Day	57% 8% 16% 12% 7%	3138
	11th to 20th	Day	56% 8% 15% 19% 2	3352
	21st to end	Day	59% 10% 12% 11% 8%	4098
April	1st to 10th	Day	70% 8% 12% 8% 2	2280
	11th to 20th	Day	62% 8% 14% 14% 2	2367
	21st to end	Day	61% 8% 16% 13% 2	2660
May	1st to 10th	Day	56% 7% 18% 15% 4	4420
	11th to 20th	Day	58% 9% 16% 13% 4	4443
	21st to end	Day	66% 8% 13% 10% 2	5440
June	1st to 10th	Day	59% 8% 14% 13% 6% 1	3040
	11th to 20th	Day	68% 8% 12% 10% 2	3040
	21st to end	Day	58% 9% 14% 15% 4 1	3040
July	1st to 10th	Day	39% 9% 10% 21% 19% 3	4981
	11th to 20th	Day	34% 8% 17% 29% 11% 1	4859
	21st to end	Day	47% 11% 16% 14% 11% 1	4841
August	1st to 10th	Day	34% 8% 16% 29% 12%	4384
	11th to 20th	Day	42% 12% 18% 22% 6%	4372
	21st to end	Day	50% 9% 23% 15% 3	4462
September	1st to 10th	Day	56% 6% 16% 16% 6% 1	2280
	11th to 20th	Day	52% 8% 17% 16% 6% 1	2280
	21st to end	Day	61% 7% 13% 12% 5% 1	2034
October	1st to 10th	Day	55% 14% 18% 10% 2	3180
	11th to 20th	Day	58% 9% 23% 10% 1	3012
	21st to end	Day	54% 11% 25% 9% 2	3048
November	1st to 10th	Day	67% 9% 12% 9% 3 1	1568
	11th to 20th	Day	65% 11% 13% 7% 4 1	1480
	21st to end	Day	66% 11% 11% 6% 5% 2	1400
December	1st to 10th	Day	63% 14% 14% 7% 2	2009
	11th to 20th	Day	61% 11% 17% 9% 3	2264
	21st to end	Day	54% 10% 24% 10% 2	2992
January	1st to 10th	Night	62% 14% 14% 8% 2	7226
	11th to 20th	Night	59% 10% 11% 8% 8% 3	6801
	21st to end	Night	65% 11% 15% 8% 2	7164
February	1st to 10th	Night	68% 6% 9% 9% 9%	2730
	11th to 20th	Night	66% 7% 11% 11% 5%	2437
	21st to end	Night	60% 6% 12% 15% 6% 1	1979
March	1st to 10th	Night	54% 10% 14% 14% 7%	3736
	11th to 20th	Night	57% 7% 16% 17% 3	3628
	21st to end	Night	48% 9% 18% 16% 9%	3554
April	1st to 10th	Night	58% 8% 17% 13% 4	1900
	11th to 20th	Night	51% 10% 17% 17% 4	1758
	21st to end	Night	55% 8% 14% 18% 4	1520
May	1st to 10th	Night	51% 8% 20% 17% 4	2540
	11th to 20th	Night	51% 9% 18% 16% 6%	2453
	21st to end	Night	62% 8% 15% 13% 2	2133
June	1st to 10th	Night	52% 8% 16% 17% 7%	1140
	11th to 20th	Night	59% 8% 19% 12% 2	1140
	21st to end	Night	47% 10% 22% 16% 5%	1140
July	1st to 10th	Night	36% 8% 14% 25% 16% 1	1870
	11th to 20th	Night	31% 7% 16% 35% 10% 1	1976
	21st to end	Night	39% 12% 20% 19% 9% 1	2458
August	1st to 10th	Night	30% 9% 21% 33% 6%	2521
	11th to 20th	Night	36% 12% 23% 26% 4	2521
	21st to end	Night	49% 11% 28% 10% 3	3204
September	1st to 10th	Night	51% 7% 16% 19% 5% 2	1900
	11th to 20th	Night	46% 7% 15% 25% 6% 1	1900
	21st to end	Night	55% 9% 15% 14% 7%	2142
October	1st to 10th	Night	53% 15% 18% 12% 3	3800
	11th to 20th	Night	51% 12% 24% 12% 2	3921
	21st to end	Night	53% 14% 23% 7% 3	4507
November	1st to 10th	Night	70% 10% 11% 7% 2	2730
	11th to 20th	Night	67% 10% 11% 7% 4 1	2899
	21st to end	Night	68% 9% 11% 7% 5% 1	3000
December	1st to 10th	Night	59% 17% 14% 7% 3	5154
	11th to 20th	Night	62% 12% 15% 8% 3	5927
	21st to end	Night	55% 11% 22% 10% 2	7964

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	11% 18% 37% 27% 6% 2	200
	11th to 20th	Day	21% 16% 36% 22% 4 2	200
	21st to end	Day	19% 20% 37% 17% 5% 2	220
February	1st to 10th	Day	22% 18% 35% 17% 7%	190
	11th to 20th	Day	18% 21% 36% 18% 7% 1	331
	21st to end	Day	10% 24% 38% 18% 8% 1	337
March	1st to 10th	Day	15% 20% 33% 22% 9%	460
	11th to 20th	Day	12% 22% 36% 20% 8% 1	460
	21st to end	Day	17% 23% 28% 20% 10% 2	506
April	1st to 10th	Day	20% 20% 33% 23% 5% 1	460
	11th to 20th	Day	16% 21% 30% 23% 8% 2	452
	21st to end	Day	19% 21% 29% 20% 9% 2	460
May	1st to 10th	Day	21% 18% 25% 23% 11% 1	463
	11th to 20th	Day	15% 10% 26% 30% 17% 2	525
	21st to end	Day	18% 12% 23% 26% 17% 3	895
June	1st to 10th	Day	20% 14% 31% 26% 8%	870
	11th to 20th	Day	29% 11% 25% 22% 12% 1	870
	21st to end	Day	23% 11% 24% 27% 13% 2	870
July	1st to 10th	Day	20% 8% 28% 30% 13% 1	856
	11th to 20th	Day	19% 10% 28% 29% 13% 1	790
	21st to end	Day	18% 12% 26% 33% 10% 1	662
August	1st to 10th	Day	12% 11% 28% 33% 13% 3	487
	11th to 20th	Day	18% 13% 32% 26% 10% 1	477
	21st to end	Day	22% 13% 31% 22% 11% 1	539
September	1st to 10th	Day	24% 15% 26% 23% 11% 2	490
	11th to 20th	Day	21% 12% 29% 25% 12% 1	490
	21st to end	Day	33% 18% 27% 16% 6% 1	490
October	1st to 10th	Day	26% 16% 26% 22% 8% 1	490
	11th to 20th	Day	27% 18% 30% 18% 6% 1	405
	21st to end	Day	24% 15% 35% 20% 4 2	314
November	1st to 10th	Day	31% 19% 31% 16% 4 1	200
	11th to 20th	Day	20% 20% 37% 16% 7% 1	200
	21st to end	Day	19% 16% 37% 18% 6% 6%	200
December	1st to 10th	Day	13% 14% 39% 22% 11% 2	200
	11th to 20th	Day	18% 16% 34% 24% 6% 3	200
	21st to end	Day	9% 22% 40% 15% 12% 1	220
January	1st to 10th	Night	20% 15% 38% 21% 5% 1	1100
	11th to 20th	Night	23% 15% 39% 19% 4 1	908
	21st to end	Night	21% 16% 38% 20% 4	927
February	1st to 10th	Night	24% 14% 34% 22% 6%	780
	11th to 20th	Night	18% 10% 39% 25% 8%	744
	21st to end	Night	11% 10% 38% 29% 12% 1	628
March	1st to 10th	Night	13% 14% 37% 25% 11%	760
	11th to 20th	Night	11% 14% 39% 24% 10% 1	760
	21st to end	Night	14% 10% 34% 29% 12% 1	836
April	1st to 10th	Night	15% 11% 28% 31% 13% 1	760
	11th to 20th	Night	11% 9% 33% 30% 15% 1	630
	21st to end	Night	20% 10% 28% 27% 15% 1	380
May	1st to 10th	Night	19% 6% 25% 32% 19%	380
	11th to 20th	Night	18% 6% 22% 33% 20% 2	374
	21st to end	Night	17% 7% 23% 28% 22% 2	411
June	1st to 10th	Night	21% 5% 23% 35% 15% 1	380
	11th to 20th	Night	28% 3 22% 28% 17% 1	380
	21st to end	Night	16% 6% 23% 31% 22% 2	380
July	1st to 10th	Night	20% 4 21% 33% 22% 1	370
	11th to 20th	Night	19% 4 18% 34% 24% 1	368
	21st to end	Night	15% 4 14% 40% 26% 1	416
August	1st to 10th	Night	12% 4 17% 36% 30% 2	378
	11th to 20th	Night	15% 4 16% 39% 23% 2	376
	21st to end	Night	25% 7% 20% 30% 17%	659
September	1st to 10th	Night	24% 5% 22% 34% 14% 1	760
	11th to 20th	Night	18% 9% 19% 33% 20% 2	760
	21st to end	Night	33% 10% 24% 21% 11% 1	760
October	1st to 10th	Night	26% 9% 25% 28% 11% 1	760
	11th to 20th	Night	22% 11% 34% 24% 9%	760
	21st to end	Night	26% 14% 33% 21% 6% 1	836
November	1st to 10th	Night	27% 16% 32% 19% 6%	780
	11th to 20th	Night	23% 19% 35% 18% 5%	899
	21st to end	Night	21% 16% 37% 19% 5% 1	1000
December	1st to 10th	Night	18% 12% 41% 22% 6% 1	1080
	11th to 20th	Night	19% 15% 40% 20% 6%	1100
	21st to end	Night	14% 17% 41% 21% 7%	1210

Page generated at 2025-02-03 00:05:53. Version ac07

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