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 2024-02-05.

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	10% 13% 6% 11% 9% 5% 6% 6% 6% 7% 21%	77386
	Night	8% 14% 6% 11% 9% 5% 7% 6% 6% 7% 20%	81425
Transparency	Day	60% 8% 14% 12% 4 1	77080
	Night	60% 9% 14% 12% 4 1	81311
Seeing	Day	20% 15% 29% 24% 10% 2	15128
	Night	20% 11% 32% 25% 11% 1	23476

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	4 14% 7% 16% 16% 7% 8% 7% 5% 7% 8%	1908
	11th to 20th	Day	5% 13% 8% 14% 8% 4 5% 6% 4 7% 27%	2199
	21st to end	Day	8% 14% 6% 12% 12% 6% 7% 8% 6% 8% 14%	2638
February	1st to 10th	Day	6% 18% 8% 13% 8% 5% 6% 6% 5% 6% 18%	1472
	11th to 20th	Day	5% 18% 10% 15% 9% 5% 7% 6% 5% 5% 15%	1543
	21st to end	Day	2 12% 7% 17% 13% 5% 7% 5% 5% 6% 22%	1390
March	1st to 10th	Day	2 13% 7% 12% 10% 6% 9% 8% 6% 7% 20%	1800
	11th to 20th	Day	3 12% 8% 13% 10% 6% 6% 7% 5% 8% 20%	1894
	21st to end	Day	3 18% 9% 14% 12% 5% 8% 5% 5% 6% 15%	2335
April	1st to 10th	Day	4 18% 9% 16% 10% 6% 7% 6% 6% 6% 12%	2160
	11th to 20th	Day	5% 17% 8% 12% 10% 5% 7% 5% 6% 6% 20%	2240
	21st to end	Day	7% 16% 7% 12% 8% 5% 6% 5% 6% 7% 21%	2520
May	1st to 10th	Day	12% 18% 6% 11% 8% 5% 5% 4 4 6% 20%	2520
	11th to 20th	Day	10% 10% 4 9% 9% 5% 6% 6% 6% 8% 27%	2512
	21st to end	Day	14% 12% 5% 9% 7% 4 6% 7% 7% 8% 23%	3069
June	1st to 10th	Day	16% 11% 5% 8% 9% 5% 6% 6% 6% 7% 22%	2880
	11th to 20th	Day	21% 14% 6% 10% 8% 5% 6% 5% 6% 5% 14%	2880
	21st to end	Day	16% 11% 5% 9% 7% 4 6% 5% 6% 7% 23%	2880
July	1st to 10th	Day	18% 8% 4 7% 7% 5% 6% 5% 6% 7% 26%	2880
	11th to 20th	Day	13% 9% 4 8% 8% 5% 6% 6% 6% 7% 27%	2822
	21st to end	Day	12% 7% 3 8% 8% 4 6% 5% 6% 8% 34%	2866
August	1st to 10th	Day	10% 8% 4 7% 8% 5% 7% 6% 7% 7% 31%	2507
	11th to 20th	Day	11% 9% 3 8% 7% 5% 6% 6% 6% 7% 33%	2475
	21st to end	Day	17% 10% 5% 9% 9% 5% 6% 6% 6% 6% 22%	2542
September	1st to 10th	Day	15% 12% 4 9% 9% 4 5% 4 5% 6% 27%	2160
	11th to 20th	Day	13% 11% 4 8% 7% 4 6% 5% 5% 7% 30%	2160
	21st to end	Day	17% 13% 4 9% 8% 5% 5% 5% 4 6% 23%	1928
October	1st to 10th	Day	14% 14% 4 10% 6% 5% 5% 5% 5% 7% 26%	1800
	11th to 20th	Day	12% 16% 5% 12% 8% 6% 6% 5% 5% 7% 19%	1720
	21st to end	Day	10% 19% 6% 11% 7% 4 5% 6% 6% 5% 19%	1755
November	1st to 10th	Day	10% 19% 7% 12% 9% 5% 7% 5% 7% 5% 14%	1488
	11th to 20th	Day	6% 14% 8% 13% 11% 5% 9% 7% 6% 6% 15%	1406
	21st to end	Day	5% 18% 8% 13% 11% 6% 7% 7% 5% 6% 14%	1330
December	1st to 10th	Day	7% 15% 7% 14% 10% 5% 6% 6% 5% 7% 18%	1175
	11th to 20th	Day	3 22% 8% 13% 9% 6% 8% 6% 7% 6% 11%	1442
	21st to end	Day	3 15% 6% 10% 9% 6% 8% 8% 9% 9% 18%	2090
January	1st to 10th	Night	4 15% 8% 15% 14% 6% 9% 8% 7% 6% 8%	5046
	11th to 20th	Night	5% 13% 8% 12% 10% 6% 7% 7% 6% 5% 20%	4720
	21st to end	Night	6% 22% 8% 15% 12% 5% 7% 5% 5% 5% 9%	5018
February	1st to 10th	Night	7% 19% 9% 13% 10% 5% 6% 5% 6% 7% 15%	2582
	11th to 20th	Night	6% 17% 10% 14% 10% 4 6% 6% 6% 7% 14%	2303
	21st to end	Night	2 12% 8% 15% 10% 5% 7% 5% 6% 7% 22%	1866
March	1st to 10th	Night	3 13% 6% 11% 11% 6% 7% 7% 8% 8% 21%	2160
	11th to 20th	Night	2 11% 7% 11% 10% 6% 10% 8% 7% 9% 19%	2065
	21st to end	Night	3 15% 6% 12% 9% 4 7% 6% 7% 8% 21%	2020
April	1st to 10th	Night	4 15% 7% 11% 9% 5% 8% 6% 6% 8% 22%	1800
	11th to 20th	Night	3 11% 6% 9% 9% 5% 7% 8% 7% 9% 25%	1666
	21st to end	Night	9% 15% 5% 10% 7% 5% 7% 5% 5% 6% 26%	1440
May	1st to 10th	Night	10% 15% 5% 9% 9% 4 5% 5% 6% 8% 23%	1440
	11th to 20th	Night	11% 9% 3 6% 7% 3 5% 6% 7% 9% 34%	1381
	21st to end	Night	12% 11% 3 7% 6% 5% 5% 6% 7% 9% 29%	1203
June	1st to 10th	Night	14% 9% 4 8% 6% 4 6% 6% 6% 7% 29%	1080
	11th to 20th	Night	20% 11% 5% 8% 7% 4 5% 5% 7% 8% 20%	1080
	21st to end	Night	13% 6% 3 8% 5% 4 7% 6% 8% 9% 31%	1080
July	1st to 10th	Night	16% 7% 4 6% 6% 4 6% 5% 6% 8% 31%	1080
	11th to 20th	Night	13% 7% 3 7% 6% 4 7% 7% 6% 8% 32%	1136
	21st to end	Night	12% 6% 2 4 6% 3 7% 6% 6% 8% 42%	1451
August	1st to 10th	Night	10% 6% 2 7% 8% 5% 5% 6% 6% 9% 37%	1432
	11th to 20th	Night	10% 6% 3 5% 5% 3 5% 5% 6% 8% 43%	1424
	21st to end	Night	17% 9% 4 8% 7% 4 6% 6% 6% 7% 27%	1812
September	1st to 10th	Night	17% 9% 4 8% 7% 4 5% 5% 4 7% 30%	1800
	11th to 20th	Night	14% 10% 4 7% 7% 3 4 4 5% 6% 37%	1800
	21st to end	Night	20% 11% 4 7% 6% 3 5% 5% 5% 7% 29%	2028
October	1st to 10th	Night	13% 13% 4 8% 6% 4 6% 5% 5% 8% 28%	2160
	11th to 20th	Night	11% 15% 4 9% 9% 5% 7% 6% 6% 8% 20%	2240
	21st to end	Night	10% 19% 6% 10% 8% 5% 6% 5% 5% 7% 19%	2600
November	1st to 10th	Night	12% 18% 6% 12% 10% 7% 7% 6% 5% 5% 12%	2590
	11th to 20th	Night	7% 16% 8% 13% 11% 6% 8% 7% 6% 5% 13%	2754
	21st to end	Night	6% 19% 8% 13% 9% 5% 7% 6% 7% 7% 12%	2850
December	1st to 10th	Night	7% 14% 7% 14% 11% 7% 7% 7% 6% 8% 13%	3002
	11th to 20th	Night	5% 19% 9% 15% 12% 6% 7% 6% 5% 6% 11%	3750
	21st to end	Night	3 14% 6% 12% 10% 6% 8% 7% 9% 9% 18%	5566

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	71% 11% 10% 5% 2	1908
	11th to 20th	Day	57% 9% 7% 11% 10% 7%	2220
	21st to end	Day	65% 14% 12% 6% 3	2638
February	1st to 10th	Day	66% 6% 11% 7% 8% 1	1472
	11th to 20th	Day	68% 6% 12% 9% 3 1	1552
	21st to end	Day	62% 7% 11% 13% 6% 3	1390
March	1st to 10th	Day	60% 8% 13% 12% 6% 1	1800
	11th to 20th	Day	61% 8% 15% 13% 4	1894
	21st to end	Day	70% 8% 13% 7% 1	2335
April	1st to 10th	Day	71% 8% 12% 8% 2	2160
	11th to 20th	Day	63% 7% 15% 13% 2	2240
	21st to end	Day	61% 8% 16% 13% 2	2520
May	1st to 10th	Day	64% 7% 14% 12% 3	2520
	11th to 20th	Day	53% 9% 17% 15% 6%	2515
	21st to end	Day	57% 9% 16% 14% 4	3070
June	1st to 10th	Day	58% 7% 14% 13% 6% 1	2880
	11th to 20th	Day	70% 8% 12% 9% 2	2880
	21st to end	Day	58% 9% 14% 15% 4 1	2880
July	1st to 10th	Day	53% 9% 13% 18% 7%	2801
	11th to 20th	Day	53% 9% 17% 17% 5%	2735
	21st to end	Day	45% 7% 20% 21% 6%	2707
August	1st to 10th	Day	49% 9% 19% 16% 6% 1	2490
	11th to 20th	Day	48% 8% 19% 19% 5% 1	2475
	21st to end	Day	59% 7% 16% 12% 5%	2542
September	1st to 10th	Day	58% 6% 16% 15% 4 1	2160
	11th to 20th	Day	52% 8% 18% 16% 6% 1	2160
	21st to end	Day	61% 7% 12% 13% 6% 1	1928
October	1st to 10th	Day	58% 7% 19% 13% 3	1800
	11th to 20th	Day	62% 7% 18% 12% 1	1720
	21st to end	Day	64% 6% 15% 11% 3	1755
November	1st to 10th	Day	69% 8% 11% 8% 3 1	1488
	11th to 20th	Day	67% 10% 12% 6% 4 1	1406
	21st to end	Day	67% 10% 10% 5% 6% 2	1330
December	1st to 10th	Day	65% 8% 12% 12% 3	1175
	11th to 20th	Day	70% 10% 9% 8% 3	1444
	21st to end	Day	56% 9% 22% 9% 3	2090
January	1st to 10th	Night	66% 14% 10% 7% 2 1	5046
	11th to 20th	Night	60% 8% 8% 8% 11% 5%	4761
	21st to end	Night	75% 9% 8% 6% 2	5018
February	1st to 10th	Night	69% 5% 8% 9% 8%	2582
	11th to 20th	Night	68% 7% 11% 11% 3	2305
	21st to end	Night	59% 6% 12% 15% 6% 1	1866
March	1st to 10th	Night	58% 8% 15% 12% 7% 1	2160
	11th to 20th	Night	58% 10% 16% 13% 3	2066
	21st to end	Night	57% 10% 19% 12% 3	2020
April	1st to 10th	Night	57% 8% 17% 13% 4	1800
	11th to 20th	Night	52% 10% 18% 17% 4	1666
	21st to end	Night	55% 8% 14% 18% 4	1440
May	1st to 10th	Night	56% 8% 17% 16% 2	1440
	11th to 20th	Night	44% 8% 19% 21% 8%	1381
	21st to end	Night	49% 8% 20% 18% 3 1	1203
June	1st to 10th	Night	52% 8% 16% 17% 7%	1080
	11th to 20th	Night	61% 7% 19% 11% 2	1080
	21st to end	Night	47% 9% 22% 17% 5%	1080
July	1st to 10th	Night	48% 9% 17% 18% 8%	1050
	11th to 20th	Night	49% 9% 19% 19% 4	1100
	21st to end	Night	36% 9% 22% 25% 7%	1370
August	1st to 10th	Night	41% 10% 21% 22% 6%	1424
	11th to 20th	Night	37% 8% 23% 26% 6%	1424
	21st to end	Night	54% 9% 18% 14% 6%	1812
September	1st to 10th	Night	54% 7% 16% 18% 4 2	1800
	11th to 20th	Night	46% 6% 15% 25% 7% 1	1800
	21st to end	Night	55% 9% 15% 14% 7%	2028
October	1st to 10th	Night	53% 8% 19% 17% 4	2160
	11th to 20th	Night	60% 8% 16% 14% 2	2240
	21st to end	Night	63% 8% 13% 12% 4	2600
November	1st to 10th	Night	71% 9% 10% 7% 2	2590
	11th to 20th	Night	69% 10% 10% 6% 4 1	2754
	21st to end	Night	69% 8% 11% 6% 5% 1	2850
December	1st to 10th	Night	66% 8% 9% 11% 5%	3002
	11th to 20th	Night	70% 9% 11% 7% 3	3747
	21st to end	Night	58% 10% 20% 9% 2	5566

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% 38% 27% 5% 2	180
	11th to 20th	Day	21% 16% 36% 21% 4 2	180
	21st to end	Day	20% 20% 36% 17% 5% 3	198
February	1st to 10th	Day	24% 19% 37% 14% 6%	168
	11th to 20th	Day	19% 22% 36% 17% 5%	303
	21st to end	Day	10% 25% 39% 18% 8% 1	306
March	1st to 10th	Day	15% 20% 33% 21% 9%	420
	11th to 20th	Day	13% 23% 35% 20% 9% 1	420
	21st to end	Day	18% 24% 28% 19% 10% 2	462
April	1st to 10th	Day	19% 20% 32% 24% 5% 1	420
	11th to 20th	Day	17% 22% 29% 21% 9% 2	412
	21st to end	Day	20% 21% 29% 20% 9% 2	420
May	1st to 10th	Day	22% 18% 26% 23% 10% 1	423
	11th to 20th	Day	15% 8% 25% 31% 18% 2	483
	21st to end	Day	18% 10% 23% 27% 17% 4	831
June	1st to 10th	Day	20% 13% 31% 27% 9%	810
	11th to 20th	Day	30% 10% 25% 22% 11% 1	810
	21st to end	Day	23% 10% 24% 27% 13% 2	810
July	1st to 10th	Day	20% 8% 27% 29% 14% 1	796
	11th to 20th	Day	20% 10% 27% 29% 12% 1	734
	21st to end	Day	17% 11% 26% 34% 10% 1	612
August	1st to 10th	Day	13% 11% 29% 32% 12% 3	447
	11th to 20th	Day	18% 12% 32% 26% 10% 1	437
	21st to end	Day	22% 13% 31% 22% 11% 1	495
September	1st to 10th	Day	26% 14% 25% 23% 10% 2	450
	11th to 20th	Day	22% 12% 28% 25% 11% 1	450
	21st to end	Day	31% 18% 27% 16% 7% 1	450
October	1st to 10th	Day	26% 14% 26% 23% 9% 2	450
	11th to 20th	Day	26% 17% 30% 18% 7% 1	370
	21st to end	Day	25% 15% 33% 20% 5% 2	283
November	1st to 10th	Day	31% 17% 32% 16% 4 1	180
	11th to 20th	Day	19% 19% 39% 14% 7% 1	180
	21st to end	Day	19% 17% 36% 18% 6% 4	180
December	1st to 10th	Day	12% 13% 39% 22% 12% 2	180
	11th to 20th	Day	19% 15% 33% 24% 6% 3	180
	21st to end	Day	10% 22% 42% 15% 10% 2	198
January	1st to 10th	Night	21% 15% 38% 21% 4 1	1040
	11th to 20th	Night	23% 14% 39% 19% 4 1	858
	21st to end	Night	21% 16% 37% 20% 5%	879
February	1st to 10th	Night	26% 14% 34% 21% 6%	738
	11th to 20th	Night	19% 10% 39% 25% 6%	704
	21st to end	Night	10% 9% 39% 29% 12% 1	592
March	1st to 10th	Night	14% 13% 38% 25% 10%	720
	11th to 20th	Night	11% 15% 40% 23% 9% 1	720
	21st to end	Night	14% 10% 34% 28% 12% 2	792
April	1st to 10th	Night	15% 11% 27% 32% 13% 2	720
	11th to 20th	Night	11% 8% 33% 30% 16% 1	598
	21st to end	Night	21% 10% 27% 26% 14% 1	360
May	1st to 10th	Night	19% 6% 25% 30% 19%	360
	11th to 20th	Night	18% 5% 21% 34% 21% 2	354
	21st to end	Night	18% 5% 22% 29% 23% 2	389
June	1st to 10th	Night	21% 4 23% 36% 16% 1	360
	11th to 20th	Night	29% 3 21% 28% 17% 1	360
	21st to end	Night	17% 5% 22% 31% 23% 2	360
July	1st to 10th	Night	21% 3 21% 33% 22% 1	350
	11th to 20th	Night	20% 4 18% 32% 24% 1	348
	21st to end	Night	15% 3 13% 41% 26% 2	394
August	1st to 10th	Night	12% 4 17% 36% 29% 2	358
	11th to 20th	Night	16% 4 17% 40% 22% 2	356
	21st to end	Night	25% 7% 20% 29% 18%	624
September	1st to 10th	Night	25% 5% 22% 32% 15% 1	720
	11th to 20th	Night	19% 8% 18% 33% 20% 2	720
	21st to end	Night	33% 10% 24% 21% 11% 1	720
October	1st to 10th	Night	26% 8% 25% 28% 11% 1	720
	11th to 20th	Night	23% 11% 32% 24% 9%	720
	21st to end	Night	27% 13% 33% 20% 6% 1	792
November	1st to 10th	Night	27% 16% 32% 19% 6%	740
	11th to 20th	Night	23% 19% 35% 18% 5%	854
	21st to end	Night	22% 17% 37% 19% 4 1	950
December	1st to 10th	Night	18% 12% 41% 23% 6% 1	1022
	11th to 20th	Night	19% 15% 40% 20% 6%	1040
	21st to end	Night	14% 16% 42% 22% 6%	1144

Page generated at 2024-02-02 02:20:27. Version ac07

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