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 2024-11-04.

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	22% 20% 5% 9% 5% 4 4 3 4 5% 19%	106300
	Night	18% 24% 6% 11% 5% 4 4 3 4 5% 17%	101236
Transparency	Day	69% 7% 10% 10% 4 1	106007
	Night	71% 6% 7% 10% 5% 1	101177
Seeing	Day	33% 10% 18% 20% 15% 4	17035
	Night	36% 11% 20% 20% 12% 2	23239

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	9% 22% 6% 13% 6% 4 4 1 3 6% 25%	1704
	11th to 20th	Day	11% 30% 5% 8% 3 3 2 1 2 5% 30%	1882
	21st to end	Day	11% 32% 8% 13% 6% 5% 4 3 3 4 11%	2222
February	1st to 10th	Day	8% 25% 7% 10% 6% 4 4 3 5% 5% 23%	1377
	11th to 20th	Day	10% 29% 6% 11% 5% 4 4 2 4 5% 19%	1496
	21st to end	Day	7% 26% 5% 8% 4 3 2 3 6% 6% 29%	1413
March	1st to 10th	Day	3 23% 6% 10% 6% 8% 7% 4 4 6% 24%	3089
	11th to 20th	Day	6% 29% 6% 15% 6% 5% 5% 3 4 6% 16%	3317
	21st to end	Day	6% 23% 5% 8% 5% 5% 4 3 5% 6% 29%	4101
April	1st to 10th	Day	9% 31% 7% 11% 6% 6% 4 3 3 4 16%	2283
	11th to 20th	Day	9% 24% 5% 9% 6% 4 5% 3 5% 6% 23%	2597
	21st to end	Day	16% 26% 4 9% 5% 5% 5% 3 5% 5% 18%	2660
May	1st to 10th	Day	16% 22% 7% 10% 5% 4 4 3 4 6% 20%	4784
	11th to 20th	Day	11% 22% 6% 12% 6% 5% 6% 4 4 5% 19%	5013
	21st to end	Day	15% 16% 5% 11% 5% 5% 4 3 5% 8% 23%	5509
June	1st to 10th	Day	25% 16% 4 10% 6% 5% 5% 3 6% 5% 15%	3247
	11th to 20th	Day	29% 15% 4 10% 5% 4 3 3 5% 6% 17%	3420
	21st to end	Day	31% 12% 3 8% 5% 5% 5% 4 5% 6% 16%	3420
July	1st to 10th	Day	24% 12% 4 9% 6% 5% 5% 4 5% 5% 20%	5395
	11th to 20th	Day	44% 18% 3 7% 3 2 2 2 4 4 10%	5124
	21st to end	Day	39% 21% 4 6% 3 2 3 2 3 3 14%	5486
August	1st to 10th	Day	25% 9% 3 7% 3 3 3 3 4 5% 36%	4810
	11th to 20th	Day	35% 13% 3 7% 3 3 3 2 3 3 26%	4340
	21st to end	Day	42% 19% 4 8% 3 3 2 2 2 3 12%	4825
September	1st to 10th	Day	50% 12% 3 6% 3 3 3 2 3 3 12%	2294
	11th to 20th	Day	41% 14% 4 7% 4 3 2 2 4 4 16%	2280
	21st to end	Day	44% 17% 4 9% 4 3 2 2 3 2 9%	2021
October	1st to 10th	Day	25% 24% 6% 12% 6% 4 3 2 3 3 12%	3170
	11th to 20th	Day	27% 27% 5% 10% 4 3 3 3 3 3 13%	2885
	21st to end	Day	18% 22% 5% 12% 5% 5% 4 3 3 5% 17%	2768
November	1st to 10th	Day	16% 29% 7% 7% 4 3 3 3 4 6% 17%	1375
	11th to 20th	Day	16% 26% 5% 10% 5% 5% 4 3 4 6% 16%	1212
	21st to end	Day	16% 27% 9% 13% 5% 5% 3 2 4 5% 10%	1140
December	1st to 10th	Day	15% 25% 5% 11% 6% 4 4 3 5% 8% 15%	1024
	11th to 20th	Day	9% 28% 6% 9% 5% 4 5% 4 4 9% 16%	1067
	21st to end	Day	14% 34% 8% 13% 5% 4 3 2 3 5% 9%	1550
January	1st to 10th	Night	9% 23% 6% 11% 5% 4 4 2 4 6% 25%	5238
	11th to 20th	Night	11% 26% 6% 9% 4 3 2 2 2 5% 32%	5016
	21st to end	Night	15% 33% 7% 12% 5% 4 4 3 3 4 9%	5437
February	1st to 10th	Night	11% 25% 6% 10% 5% 4 3 3 5% 6% 22%	2802
	11th to 20th	Night	11% 30% 7% 11% 6% 4 3 2 4 5% 17%	2568
	21st to end	Night	8% 23% 6% 8% 6% 4 4 4 4 7% 24%	2041
March	1st to 10th	Night	4 23% 6% 12% 6% 6% 7% 3 5% 5% 23%	3774
	11th to 20th	Night	7% 27% 8% 14% 6% 6% 5% 4 5% 4 15%	3643
	21st to end	Night	10% 20% 5% 11% 5% 5% 4 3 5% 7% 25%	3526
April	1st to 10th	Night	11% 29% 7% 11% 5% 5% 5% 3 5% 4 15%	1895
	11th to 20th	Night	9% 23% 6% 11% 5% 5% 5% 3 5% 5% 23%	1532
	21st to end	Night	18% 25% 5% 10% 5% 3 3 3 5% 4 18%	1520
May	1st to 10th	Night	17% 23% 5% 10% 5% 4 2 2 4 5% 23%	2176
	11th to 20th	Night	14% 19% 8% 15% 6% 4 4 4 6% 5% 17%	1882
	21st to end	Night	14% 16% 7% 15% 6% 4 5% 4 6% 6% 16%	2066
June	1st to 10th	Night	29% 16% 5% 11% 5% 4 2 2 4 5% 17%	931
	11th to 20th	Night	31% 15% 4 8% 5% 3 4 3 5% 6% 18%	760
	21st to end	Night	33% 11% 3 10% 3 4 4 4 6% 6% 17%	760
July	1st to 10th	Night	23% 14% 5% 14% 4 4 4 3 4 6% 19%	1562
	11th to 20th	Night	38% 23% 4 9% 3 2 3 2 3 3 11%	1835
	21st to end	Night	40% 20% 4 9% 3 2 3 2 3 3 13%	2066
August	1st to 10th	Night	24% 12% 2 7% 3 2 2 2 5% 4 36%	2124
	11th to 20th	Night	32% 13% 3 8% 4 3 3 2 3 5% 23%	2498
	21st to end	Night	43% 18% 3 7% 2 2 2 2 2 4 15%	2842
September	1st to 10th	Night	46% 14% 4 7% 4 3 3 2 3 2 10%	1886
	11th to 20th	Night	37% 15% 4 8% 3 4 2 2 2 4 17%	1900
	21st to end	Night	45% 16% 4 9% 4 3 3 2 2 3 9%	2155
October	1st to 10th	Night	28% 23% 6% 14% 4 3 3 2 3 3 12%	3800
	11th to 20th	Night	25% 27% 6% 12% 5% 4 4 3 3 3 10%	4042
	21st to end	Night	18% 21% 5% 13% 6% 4 3 3 4 4 18%	4790
November	1st to 10th	Night	17% 28% 5% 10% 5% 4 3 2 4 5% 17%	2775
	11th to 20th	Night	14% 27% 6% 10% 6% 4 5% 2 3 7% 17%	2966
	21st to end	Night	14% 31% 7% 13% 5% 4 3 2 4 8% 9%	3040
December	1st to 10th	Night	16% 25% 6% 10% 5% 4 4 3 5% 8% 13%	3135
	11th to 20th	Night	10% 27% 6% 11% 5% 5% 5% 3 4 6% 18%	4120
	21st to end	Night	15% 33% 8% 13% 6% 4 3 3 3 4 10%	6133

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% 7% 5% 15% 7% 5%	1704
	11th to 20th	Day	63% 4 4 10% 14% 6%	1900
	21st to end	Day	82% 4 4 6% 4 1	2222
February	1st to 10th	Day	65% 6% 7% 9% 10% 3	1377
	11th to 20th	Day	71% 4 7% 5% 10% 3	1504
	21st to end	Day	57% 5% 10% 14% 11% 2	1413
March	1st to 10th	Day	59% 6% 7% 11% 15% 2	3089
	11th to 20th	Day	72% 8% 6% 9% 4 1	3317
	21st to end	Day	57% 7% 11% 22% 4	4101
April	1st to 10th	Day	75% 7% 4 9% 4	2283
	11th to 20th	Day	62% 9% 9% 12% 7% 1	2597
	21st to end	Day	70% 8% 9% 9% 3	2660
May	1st to 10th	Day	68% 7% 7% 14% 3	4784
	11th to 20th	Day	68% 8% 7% 12% 5%	5016
	21st to end	Day	61% 12% 12% 12% 4	5510
June	1st to 10th	Day	70% 10% 10% 7% 2	3247
	11th to 20th	Day	69% 9% 13% 9%	3420
	21st to end	Day	69% 10% 15% 5% 1	3420
July	1st to 10th	Day	60% 10% 18% 10% 2	5311
	11th to 20th	Day	80% 7% 10% 3	5035
	21st to end	Day	75% 5% 13% 7%	5313
August	1st to 10th	Day	51% 8% 15% 20% 6%	4791
	11th to 20th	Day	64% 6% 19% 11% 1	4382
	21st to end	Day	79% 5% 9% 7%	4824
September	1st to 10th	Day	80% 6% 7% 6% 1	2294
	11th to 20th	Day	74% 6% 6% 12% 3	2280
	21st to end	Day	84% 4 5% 7% 1	2021
October	1st to 10th	Day	77% 6% 10% 6% 2	3170
	11th to 20th	Day	78% 6% 6% 9% 2	2885
	21st to end	Day	70% 8% 14% 7% 1	2768
November	1st to 10th	Day	72% 6% 7% 11% 5% 1	1375
	11th to 20th	Day	73% 6% 7% 10% 4	1212
	21st to end	Day	78% 5% 6% 7% 4	1140
December	1st to 10th	Day	71% 8% 9% 8% 4	1024
	11th to 20th	Day	70% 7% 5% 9% 9%	1068
	21st to end	Day	84% 4 3 5% 4 1	1550
January	1st to 10th	Night	63% 5% 6% 17% 6% 2	5238
	11th to 20th	Night	59% 3 4 9% 12% 12%	5060
	21st to end	Night	82% 5% 5% 4 4	5437
February	1st to 10th	Night	65% 5% 7% 10% 9% 4	2802
	11th to 20th	Night	72% 4 5% 6% 10% 3	2571
	21st to end	Night	60% 5% 9% 13% 9% 3	2041
March	1st to 10th	Night	58% 4 7% 16% 13% 2	3774
	11th to 20th	Night	77% 5% 6% 9% 3	3645
	21st to end	Night	55% 9% 14% 18% 4	3526
April	1st to 10th	Night	73% 6% 7% 9% 4	1895
	11th to 20th	Night	64% 8% 8% 13% 6% 1	1532
	21st to end	Night	71% 6% 7% 11% 4	1520
May	1st to 10th	Night	66% 5% 6% 18% 4	2176
	11th to 20th	Night	68% 10% 7% 10% 5%	1882
	21st to end	Night	65% 11% 12% 11% 2	2066
June	1st to 10th	Night	72% 9% 9% 6% 4	931
	11th to 20th	Night	69% 11% 13% 7% 1	760
	21st to end	Night	67% 13% 14% 5%	760
July	1st to 10th	Night	66% 7% 19% 6% 2	1537
	11th to 20th	Night	80% 6% 10% 4	1802
	21st to end	Night	79% 5% 11% 5% 1	2000
August	1st to 10th	Night	51% 12% 13% 22% 3	2118
	11th to 20th	Night	62% 9% 18% 8% 3	2522
	21st to end	Night	77% 6% 9% 8%	2842
September	1st to 10th	Night	82% 7% 6% 4 1	1886
	11th to 20th	Night	75% 4 6% 12% 3	1900
	21st to end	Night	83% 5% 4 6% 2	2155
October	1st to 10th	Night	77% 7% 5% 10% 2	3800
	11th to 20th	Night	80% 5% 7% 7% 2	4042
	21st to end	Night	69% 7% 11% 11% 3	4790
November	1st to 10th	Night	73% 5% 7% 10% 5%	2775
	11th to 20th	Night	71% 7% 6% 10% 5% 1	2966
	21st to end	Night	78% 6% 6% 7% 4	3040
December	1st to 10th	Night	71% 7% 9% 8% 5%	3135
	11th to 20th	Night	71% 6% 5% 10% 7%	4118
	21st to end	Night	81% 5% 4 5% 4 1	6133

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	15% 16% 22% 32% 12% 3	125
	11th to 20th	Day	28% 11% 29% 18% 12% 1	180
	21st to end	Day	29% 20% 16% 19% 13% 2	278
February	1st to 10th	Day	22% 13% 31% 20% 13% 1	370
	11th to 20th	Day	24% 15% 24% 22% 13% 2	365
	21st to end	Day	20% 15% 30% 21% 10% 4	307
March	1st to 10th	Day	13% 15% 28% 25% 14% 4	370
	11th to 20th	Day	21% 18% 27% 21% 13% 1	370
	21st to end	Day	18% 14% 24% 23% 17% 5%	488
April	1st to 10th	Day	21% 15% 28% 21% 12% 2	463
	11th to 20th	Day	19% 11% 21% 23% 20% 5%	640
	21st to end	Day	26% 11% 22% 21% 17% 3	650
May	1st to 10th	Day	29% 12% 19% 21% 15% 3	653
	11th to 20th	Day	19% 10% 18% 25% 23% 5%	675
	21st to end	Day	20% 9% 17% 24% 23% 6%	735
June	1st to 10th	Day	30% 9% 17% 20% 19% 6%	783
	11th to 20th	Day	34% 6% 15% 22% 18% 4	870
	21st to end	Day	33% 7% 10% 20% 22% 8%	870
July	1st to 10th	Day	30% 5% 15% 23% 21% 5%	686
	11th to 20th	Day	45% 9% 13% 16% 15% 3	668
	21st to end	Day	47% 6% 9% 17% 18% 4	739
August	1st to 10th	Day	38% 8% 11% 21% 17% 5%	676
	11th to 20th	Day	53% 8% 10% 14% 11% 4	665
	21st to end	Day	55% 8% 10% 16% 11% 1	748
September	1st to 10th	Day	48% 7% 11% 17% 15% 2	504
	11th to 20th	Day	45% 6% 14% 20% 12% 3	490
	21st to end	Day	51% 12% 16% 11% 9% 2	443
October	1st to 10th	Day	41% 13% 17% 17% 8% 4	390
	11th to 20th	Day	47% 13% 18% 13% 5% 4	390
	21st to end	Day	33% 9% 28% 18% 10% 2	429
November	1st to 10th	Day	32% 12% 30% 13% 11% 2	238
	11th to 20th	Day	34% 16% 21% 18% 9% 2	180
	21st to end	Day	31% 16% 29% 14% 9% 1	180
December	1st to 10th	Day	32% 12% 21% 21% 12% 2	180
	11th to 20th	Day	30% 9% 22% 18% 18% 2	138
	21st to end	Day	22% 14% 30% 21% 9% 3	99
January	1st to 10th	Night	30% 12% 26% 22% 9% 1	850
	11th to 20th	Night	33% 19% 25% 15% 7% 1	850
	21st to end	Night	34% 16% 20% 19% 9% 1	935
February	1st to 10th	Night	27% 13% 26% 24% 9% 2	850
	11th to 20th	Night	28% 13% 26% 23% 9% 1	834
	21st to end	Night	20% 12% 29% 27% 11% 1	703
March	1st to 10th	Night	19% 14% 28% 23% 15% 1	771
	11th to 20th	Night	24% 14% 30% 22% 9% 1	670
	21st to end	Night	23% 9% 24% 23% 18% 2	627
April	1st to 10th	Night	27% 12% 22% 21% 16% 3	570
	11th to 20th	Night	22% 9% 22% 26% 20% 1	563
	21st to end	Night	33% 10% 15% 23% 16% 3	570
May	1st to 10th	Night	39% 7% 13% 21% 15% 4	451
	11th to 20th	Night	27% 8% 17% 23% 22% 3	374
	21st to end	Night	20% 9% 15% 22% 29% 4	411
June	1st to 10th	Night	35% 11% 14% 16% 22% 3	275
	11th to 20th	Night	39% 3 14% 17% 19% 7%	190
	21st to end	Night	41% 7% 7% 15% 23% 7%	190
July	1st to 10th	Night	37% 9% 12% 18% 20% 4	185
	11th to 20th	Night	48% 8% 9% 14% 17% 5%	332
	21st to end	Night	50% 7% 8% 15% 14% 6%	416
August	1st to 10th	Night	43% 6% 10% 16% 19% 6%	503
	11th to 20th	Night	54% 7% 9% 13% 12% 5%	564
	21st to end	Night	60% 5% 9% 13% 11% 1	627
September	1st to 10th	Night	55% 8% 11% 18% 8% 1	570
	11th to 20th	Night	47% 8% 12% 17% 14% 2	570
	21st to end	Night	55% 10% 13% 13% 7% 2	738
October	1st to 10th	Night	48% 9% 17% 17% 9% 1	760
	11th to 20th	Night	54% 11% 16% 13% 6% 1	760
	21st to end	Night	38% 12% 23% 17% 9% 1	939
November	1st to 10th	Night	35% 13% 22% 20% 9% 1	847
	11th to 20th	Night	32% 14% 25% 17% 10% 2	850
	21st to end	Night	36% 16% 21% 18% 8% 1	850
December	1st to 10th	Night	34% 12% 19% 24% 10% 1	945
	11th to 20th	Night	30% 12% 25% 23% 9% 1	1040
	21st to end	Night	32% 14% 21% 21% 10% 2	1059

Page generated at 2024-11-01 18:47:50. Version ac07

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