Haines
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Haines clear sky chart from 2005-11-06 to 2026-10-29.

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	18% 19% 5% 11% 5% 5% 4 3 4 5% 19%	155799
	Night	15% 22% 6% 13% 6% 4 4 3 4 5% 18%	144884
Transparency	Day	65% 7% 13% 10% 3	155459
	Night	67% 7% 10% 11% 5% 1	144808
Seeing	Day	32% 11% 18% 20% 16% 4	19708
	Night	34% 12% 20% 20% 12% 2	25792

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	5% 18% 7% 18% 9% 7% 5% 3 4 5% 20%	3166
	11th to 20th	Day	9% 23% 5% 11% 6% 5% 4 3 5% 6% 22%	3522
	21st to end	Day	7% 26% 7% 18% 8% 5% 5% 3 4 4 16%	4129
February	1st to 10th	Day	7% 24% 7% 11% 6% 4 4 3 5% 5% 24%	1523
	11th to 20th	Day	10% 28% 6% 12% 6% 4 4 3 4 5% 19%	1658
	21st to end	Day	7% 25% 5% 10% 4 3 2 3 6% 6% 28%	1557
March	1st to 10th	Day	3 23% 6% 12% 6% 8% 7% 4 6% 5% 19%	4544
	11th to 20th	Day	4 23% 6% 13% 6% 5% 5% 3 4 5% 24%	4857
	21st to end	Day	4 18% 5% 10% 6% 5% 5% 4 6% 8% 30%	6007
April	1st to 10th	Day	8% 31% 7% 11% 6% 6% 4 3 3 4 17%	2523
	11th to 20th	Day	8% 23% 5% 11% 7% 5% 5% 4 5% 6% 22%	2874
	21st to end	Day	15% 26% 5% 10% 5% 5% 5% 3 5% 5% 17%	2940
May	1st to 10th	Day	11% 21% 8% 14% 7% 6% 5% 3 4 5% 14%	8871
	11th to 20th	Day	8% 20% 7% 16% 7% 6% 6% 4 5% 5% 17%	9352
	21st to end	Day	12% 15% 6% 14% 8% 7% 6% 4 6% 7% 16%	10305
June	1st to 10th	Day	24% 16% 5% 10% 6% 5% 5% 3 6% 5% 15%	3589
	11th to 20th	Day	27% 15% 4 10% 5% 4 3 3 4 6% 18%	3780
	21st to end	Day	29% 13% 4 8% 5% 4 5% 4 5% 6% 16%	3780
July	1st to 10th	Day	21% 15% 5% 11% 6% 5% 6% 5% 5% 5% 15%	10063
	11th to 20th	Day	27% 16% 4 9% 4 3 3 3 5% 6% 20%	9540
	21st to end	Day	26% 17% 4 8% 4 4 4 3 5% 5% 21%	10218
August	1st to 10th	Day	19% 8% 3 8% 4 4 4 4 4 5% 36%	7052
	11th to 20th	Day	29% 11% 3 9% 4 3 3 2 3 3 31%	6387
	21st to end	Day	39% 18% 4 9% 4 3 2 2 3 4 12%	7019
September	1st to 10th	Day	46% 13% 3 6% 3 2 2 2 3 4 15%	2535
	11th to 20th	Day	41% 14% 4 7% 4 3 2 2 4 4 16%	2520
	21st to end	Day	43% 18% 4 9% 5% 3 2 2 3 3 9%	2233
October	1st to 10th	Day	24% 24% 6% 12% 5% 4 3 2 3 3 13%	3370
	11th to 20th	Day	26% 27% 5% 10% 4 3 3 3 3 3 13%	3068
	21st to end	Day	17% 22% 5% 12% 5% 5% 4 3 3 5% 18%	2923
November	1st to 10th	Day	16% 30% 7% 9% 4 3 3 3 4 6% 16%	1496
	11th to 20th	Day	15% 25% 5% 12% 5% 5% 4 3 4 6% 16%	1339
	21st to end	Day	15% 26% 9% 13% 5% 4 3 2 4 5% 13%	1260
December	1st to 10th	Day	12% 26% 9% 14% 7% 4 4 4 4 5% 10%	1800
	11th to 20th	Day	6% 21% 6% 10% 8% 6% 5% 3 5% 8% 20%	1722
	21st to end	Day	12% 32% 8% 12% 5% 3 2 2 3 4 16%	2277
January	1st to 10th	Night	6% 21% 7% 16% 7% 6% 5% 3 4 5% 21%	9726
	11th to 20th	Night	8% 21% 6% 13% 7% 5% 4 3 4 5% 23%	9376
	21st to end	Night	10% 25% 7% 18% 8% 5% 4 3 3 4 15%	10051
February	1st to 10th	Night	11% 24% 6% 11% 5% 4 3 3 5% 6% 23%	3096
	11th to 20th	Night	10% 29% 7% 11% 5% 4 3 2 4 5% 19%	2846
	21st to end	Night	8% 23% 6% 10% 7% 5% 4 4 4 7% 23%	2249
March	1st to 10th	Night	3 21% 7% 17% 7% 7% 6% 3 4 4 20%	5549
	11th to 20th	Night	5% 22% 7% 14% 6% 5% 5% 4 5% 5% 21%	5328
	21st to end	Night	7% 19% 6% 12% 6% 5% 4 3 5% 7% 25%	5171
April	1st to 10th	Night	10% 28% 7% 11% 5% 5% 5% 3 5% 4 16%	2095
	11th to 20th	Night	8% 23% 6% 12% 5% 6% 5% 3 5% 5% 22%	1695
	21st to end	Night	17% 24% 5% 12% 6% 4 4 3 5% 4 18%	1680
May	1st to 10th	Night	12% 21% 8% 17% 7% 5% 4 3 5% 4 14%	4042
	11th to 20th	Night	9% 17% 8% 18% 7% 5% 4 4 6% 5% 16%	3510
	21st to end	Night	12% 16% 8% 17% 7% 5% 6% 4 6% 5% 15%	3866
June	1st to 10th	Night	27% 16% 5% 11% 5% 4 3 3 5% 5% 17%	1028
	11th to 20th	Night	30% 15% 4 8% 5% 3 5% 3 5% 6% 18%	840
	21st to end	Night	30% 12% 3 10% 3 4 4 4 6% 5% 18%	840
July	1st to 10th	Night	22% 16% 5% 18% 6% 4 5% 3 4 5% 13%	2894
	11th to 20th	Night	22% 15% 4 11% 3 3 4 2 4 6% 25%	3419
	21st to end	Night	26% 15% 4 9% 4 4 4 3 4 5% 21%	3850
August	1st to 10th	Night	18% 11% 3 10% 4 3 4 3 5% 6% 34%	3109
	11th to 20th	Night	24% 11% 3 10% 4 3 4 2 3 6% 30%	3678
	21st to end	Night	35% 21% 4 8% 3 2 3 2 2 3 17%	4128
September	1st to 10th	Night	43% 14% 4 8% 4 3 3 2 3 3 14%	2084
	11th to 20th	Night	36% 15% 4 9% 3 4 2 2 2 4 17%	2100
	21st to end	Night	42% 18% 4 9% 4 3 2 2 2 3 9%	2383
October	1st to 10th	Night	27% 23% 6% 14% 4 3 3 2 3 3 12%	4040
	11th to 20th	Night	24% 27% 6% 12% 5% 4 4 3 3 3 10%	4299
	21st to end	Night	17% 21% 5% 13% 6% 4 3 3 4 4 19%	5054
November	1st to 10th	Night	17% 28% 5% 11% 5% 4 3 2 4 4 16%	3022
	11th to 20th	Night	13% 27% 6% 11% 6% 4 5% 2 3 7% 16%	3279
	21st to end	Night	13% 29% 7% 13% 5% 4 3 2 4 7% 12%	3360
December	1st to 10th	Night	12% 29% 9% 14% 5% 3 3 3 4 5% 14%	5550
	11th to 20th	Night	8% 22% 5% 11% 7% 6% 6% 4 5% 6% 20%	6685
	21st to end	Night	12% 33% 8% 13% 5% 4 3 2 3 4 13%	8962

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	61% 10% 4 13% 10% 3	3166
	11th to 20th	Day	57% 11% 8% 11% 9% 3	3540
	21st to end	Day	74% 5% 6% 9% 6% 1	4130
February	1st to 10th	Day	63% 6% 8% 11% 10% 3	1523
	11th to 20th	Day	69% 4 7% 7% 10% 3	1666
	21st to end	Day	57% 5% 10% 14% 11% 3	1557
March	1st to 10th	Day	62% 6% 10% 10% 11% 1	4544
	11th to 20th	Day	61% 7% 5% 12% 14%	4857
	21st to end	Day	50% 6% 13% 27% 4	6007
April	1st to 10th	Day	74% 7% 5% 10% 4	2523
	11th to 20th	Day	62% 9% 9% 12% 6% 1	2874
	21st to end	Day	70% 8% 9% 10% 3	2940
May	1st to 10th	Day	68% 9% 11% 10% 2	8871
	11th to 20th	Day	67% 7% 12% 10% 3	9355
	21st to end	Day	62% 10% 13% 12% 2	10306
June	1st to 10th	Day	69% 10% 11% 8% 2	3589
	11th to 20th	Day	68% 8% 15% 9%	3780
	21st to end	Day	69% 10% 15% 5% 1	3780
July	1st to 10th	Day	63% 8% 18% 10% 1	9979
	11th to 20th	Day	62% 8% 25% 4	9451
	21st to end	Day	63% 6% 24% 7%	9997
August	1st to 10th	Day	49% 9% 22% 17% 4	7033
	11th to 20th	Day	58% 6% 25% 10% 1	6429
	21st to end	Day	76% 5% 10% 8%	7018
September	1st to 10th	Day	75% 6% 10% 8% 1	2535
	11th to 20th	Day	73% 6% 6% 12% 2	2520
	21st to end	Day	84% 3 5% 7% 1	2233
October	1st to 10th	Day	76% 6% 10% 6% 2	3370
	11th to 20th	Day	77% 6% 6% 9% 2	3068
	21st to end	Day	70% 7% 15% 7% 1	2923
November	1st to 10th	Day	72% 6% 7% 10% 4 1	1496
	11th to 20th	Day	71% 6% 7% 10% 4	1339
	21st to end	Day	75% 5% 8% 8% 5%	1260
December	1st to 10th	Day	78% 6% 7% 7% 3	1800
	11th to 20th	Day	61% 9% 11% 9% 9%	1723
	21st to end	Day	77% 4 5% 9% 4 1	2277
January	1st to 10th	Night	62% 9% 5% 14% 9% 1	9726
	11th to 20th	Night	59% 8% 9% 10% 7% 6%	9420
	21st to end	Night	73% 7% 6% 10% 4	10051
February	1st to 10th	Night	63% 5% 8% 11% 9% 4	3096
	11th to 20th	Night	70% 4 6% 8% 10% 2	2849
	21st to end	Night	61% 6% 9% 13% 9% 3	2249
March	1st to 10th	Night	61% 6% 9% 14% 9% 1	5549
	11th to 20th	Night	65% 6% 5% 12% 12%	5330
	21st to end	Night	54% 8% 12% 20% 5%	5171
April	1st to 10th	Night	72% 6% 8% 9% 4	2095
	11th to 20th	Night	63% 8% 9% 14% 6% 1	1695
	21st to end	Night	70% 7% 8% 11% 4	1680
May	1st to 10th	Night	70% 9% 6% 13% 2	4039
	11th to 20th	Night	64% 9% 14% 10% 3	3510
	21st to end	Night	63% 11% 12% 14% 1	3870
June	1st to 10th	Night	70% 10% 10% 6% 4	1028
	11th to 20th	Night	68% 10% 14% 7%	840
	21st to end	Night	66% 13% 16% 5%	840
July	1st to 10th	Night	71% 6% 17% 5% 1	2869
	11th to 20th	Night	59% 8% 28% 5%	3386
	21st to end	Night	66% 4 23% 6%	3766
August	1st to 10th	Night	50% 11% 20% 16% 2	3103
	11th to 20th	Night	55% 9% 27% 6% 2	3702
	21st to end	Night	74% 5% 10% 11%	4128
September	1st to 10th	Night	78% 7% 8% 6% 1	2084
	11th to 20th	Night	74% 4 7% 12% 2	2100
	21st to end	Night	84% 5% 4 5% 2	2383
October	1st to 10th	Night	77% 7% 5% 10% 2	4040
	11th to 20th	Night	79% 5% 7% 7% 2	4299
	21st to end	Night	69% 7% 10% 12% 3	5054
November	1st to 10th	Night	73% 6% 7% 9% 5%	3022
	11th to 20th	Night	71% 7% 6% 10% 5% 1	3279
	21st to end	Night	74% 6% 7% 9% 5%	3360
December	1st to 10th	Night	73% 5% 10% 8% 4	5550
	11th to 20th	Night	63% 8% 10% 13% 6%	6683
	21st to end	Night	78% 4 5% 8% 4 1	8962

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	16% 17% 25% 27% 12% 3	153
	11th to 20th	Day	29% 13% 28% 19% 11% 1	220
	21st to end	Day	29% 19% 17% 20% 12% 2	331
February	1st to 10th	Day	21% 13% 29% 22% 13% 1	430
	11th to 20th	Day	22% 15% 24% 23% 14% 3	425
	21st to end	Day	19% 15% 32% 21% 10% 3	355
March	1st to 10th	Day	14% 17% 26% 24% 16% 4	430
	11th to 20th	Day	18% 17% 27% 21% 15% 2	430
	21st to end	Day	16% 12% 22% 25% 19% 6%	572
April	1st to 10th	Day	21% 15% 27% 22% 13% 2	543
	11th to 20th	Day	19% 13% 21% 23% 19% 4	740
	21st to end	Day	26% 13% 22% 20% 16% 3	750
May	1st to 10th	Day	29% 12% 21% 22% 13% 3	753
	11th to 20th	Day	18% 11% 18% 24% 23% 6%	775
	21st to end	Day	21% 9% 18% 25% 22% 5%	845
June	1st to 10th	Day	29% 11% 16% 19% 19% 6%	894
	11th to 20th	Day	33% 6% 14% 24% 19% 5%	990
	21st to end	Day	32% 7% 10% 20% 23% 8%	990
July	1st to 10th	Day	30% 5% 16% 24% 20% 5%	788
	11th to 20th	Day	42% 8% 13% 18% 16% 3	768
	21st to end	Day	42% 6% 9% 18% 19% 5%	849
August	1st to 10th	Day	35% 8% 12% 22% 18% 5%	776
	11th to 20th	Day	50% 8% 10% 14% 12% 5%	765
	21st to end	Day	50% 8% 10% 17% 13% 2	858
September	1st to 10th	Day	44% 8% 11% 17% 18% 2	585
	11th to 20th	Day	45% 6% 14% 19% 12% 3	570
	21st to end	Day	51% 11% 15% 12% 9% 2	513
October	1st to 10th	Day	40% 14% 17% 18% 8% 4	450
	11th to 20th	Day	46% 14% 18% 14% 4 3	450
	21st to end	Day	32% 10% 27% 19% 11% 2	487
November	1st to 10th	Day	31% 13% 31% 13% 10% 2	274
	11th to 20th	Day	35% 15% 20% 18% 9% 3	220
	21st to end	Day	27% 16% 32% 15% 9%	220
December	1st to 10th	Day	33% 15% 21% 18% 12% 1	220
	11th to 20th	Day	26% 11% 23% 21% 16% 3	168
	21st to end	Day	25% 14% 30% 21% 7% 2	121
January	1st to 10th	Night	29% 13% 26% 23% 9% 1	950
	11th to 20th	Night	33% 20% 24% 16% 6% 1	950
	21st to end	Night	33% 16% 20% 19% 10% 1	1045
February	1st to 10th	Night	26% 13% 26% 26% 9% 1	950
	11th to 20th	Night	26% 13% 24% 25% 11% 1	934
	21st to end	Night	20% 13% 30% 27% 10% 1	783
March	1st to 10th	Night	19% 15% 27% 22% 15% 2	853
	11th to 20th	Night	23% 13% 28% 24% 10% 2	740
	21st to end	Night	21% 9% 23% 24% 20% 3	693
April	1st to 10th	Night	26% 11% 21% 22% 16% 3	630
	11th to 20th	Night	22% 10% 21% 26% 20% 1	623
	21st to end	Night	32% 11% 16% 23% 16% 3	630
May	1st to 10th	Night	38% 9% 14% 20% 14% 4	498
	11th to 20th	Night	25% 9% 16% 22% 23% 4	414
	21st to end	Night	20% 9% 16% 23% 28% 4	455
June	1st to 10th	Night	34% 11% 14% 17% 21% 3	303
	11th to 20th	Night	38% 4 12% 18% 20% 8%	210
	21st to end	Night	38% 10% 6% 14% 23% 9%	210
July	1st to 10th	Night	35% 12% 11% 19% 20% 4	205
	11th to 20th	Night	44% 8% 8% 15% 19% 7%	368
	21st to end	Night	47% 6% 7% 16% 15% 8%	460
August	1st to 10th	Night	40% 8% 10% 15% 20% 7%	557
	11th to 20th	Night	51% 7% 9% 13% 13% 7%	624
	21st to end	Night	56% 6% 9% 13% 14% 2	693
September	1st to 10th	Night	52% 8% 10% 18% 11% 2	630
	11th to 20th	Night	47% 8% 12% 17% 14% 2	630
	21st to end	Night	55% 10% 12% 13% 7% 2	816
October	1st to 10th	Night	48% 9% 16% 17% 9% 1	840
	11th to 20th	Night	53% 11% 16% 13% 6% 1	840
	21st to end	Night	36% 13% 23% 17% 9% 2	1032
November	1st to 10th	Night	36% 13% 22% 20% 8% 1	930
	11th to 20th	Night	31% 15% 24% 18% 10% 2	950
	21st to end	Night	34% 16% 22% 19% 8% 1	950
December	1st to 10th	Night	35% 14% 18% 22% 10% 1	1055
	11th to 20th	Night	28% 12% 26% 24% 9% 1	1160
	21st to end	Night	31% 15% 23% 20% 10% 2	1181

Page generated at 2026-10-26 00:37:45. Version ac07

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