Caribou
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Caribou clear sky chart from 2005-11-06 to 2025-02-21.

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	17% 9% 3 8% 5% 5% 5% 4 6% 7% 30%	108085
	Night	17% 11% 4 8% 5% 5% 5% 4 5% 6% 31%	110589
Transparency	Day	53% 3 13% 21% 9% 1	111602
	Night	55% 3 12% 21% 9% 1	115237
Seeing	Day	22% 13% 29% 23% 10% 2	16264
	Night	22% 10% 31% 28% 8% 1	24459

By Month

Percentage Cloud Cover NE (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	13% 18% 8% 12% 8% 6% 5% 3 5% 4 18%	3174
	11th to 20th	Day	11% 12% 6% 15% 7% 5% 5% 4 5% 7% 23%	3570
	21st to end	Day	6% 8% 5% 11% 6% 6% 7% 5% 7% 8% 31%	3960
February	1st to 10th	Day	11% 14% 5% 8% 7% 6% 6% 5% 7% 6% 25%	1782
	11th to 20th	Day	15% 12% 5% 10% 6% 5% 6% 4 6% 6% 25%	1768
	21st to end	Day	12% 8% 3 7% 8% 6% 7% 4 6% 7% 30%	1570
March	1st to 10th	Day	18% 11% 4 9% 5% 5% 5% 4 6% 6% 27%	3169
	11th to 20th	Day	17% 16% 5% 11% 6% 5% 5% 4 5% 5% 19%	3480
	21st to end	Day	22% 12% 4 7% 5% 4 5% 3 4 6% 27%	3816
April	1st to 10th	Day	19% 12% 3 8% 6% 6% 5% 4 5% 6% 27%	2276
	11th to 20th	Day	18% 9% 3 7% 5% 4 5% 4 6% 6% 34%	2442
	21st to end	Day	24% 10% 3 6% 4 4 4 3 5% 6% 32%	2470
May	1st to 10th	Day	17% 8% 3 8% 6% 6% 6% 4 6% 7% 29%	4106
	11th to 20th	Day	21% 9% 2 7% 4 4 5% 4 5% 7% 31%	4318
	21st to end	Day	16% 6% 3 8% 5% 6% 6% 5% 7% 8% 30%	5185
June	1st to 10th	Day	21% 9% 2 7% 5% 5% 5% 4 7% 8% 27%	2850
	11th to 20th	Day	18% 7% 2 7% 5% 4 5% 4 6% 7% 34%	2850
	21st to end	Day	22% 10% 3 7% 6% 5% 5% 4 6% 7% 25%	2850
July	1st to 10th	Day	15% 6% 2 8% 5% 6% 6% 5% 7% 10% 30%	4760
	11th to 20th	Day	16% 5% 3 7% 5% 4 5% 5% 7% 8% 35%	4676
	21st to end	Day	15% 6% 2 5% 5% 5% 5% 5% 7% 9% 38%	4814
August	1st to 10th	Day	17% 6% 2 6% 5% 6% 6% 5% 7% 8% 32%	4116
	11th to 20th	Day	16% 8% 3 8% 6% 6% 5% 4 7% 8% 29%	4045
	21st to end	Day	17% 6% 2 6% 4 5% 5% 4 6% 9% 37%	4532
September	1st to 10th	Day	16% 6% 3 6% 4 3 5% 2 6% 7% 41%	2257
	11th to 20th	Day	17% 5% 2 4 3 4 3 3 4 6% 48%	2090
	21st to end	Day	17% 6% 2 6% 4 3 4 4 5% 8% 40%	2090
October	1st to 10th	Day	17% 9% 2 6% 5% 5% 3 3 5% 7% 37%	1989
	11th to 20th	Day	21% 8% 3 7% 4 4 4 4 6% 6% 32%	1881
	21st to end	Day	24% 9% 4 8% 5% 4 5% 3 5% 7% 26%	1881
November	1st to 10th	Day	19% 11% 3 7% 5% 5% 5% 4 5% 6% 30%	1746
	11th to 20th	Day	20% 10% 3 10% 5% 5% 5% 4 5% 6% 27%	1600
	21st to end	Day	21% 12% 3 9% 5% 5% 5% 3 5% 7% 25%	1598
December	1st to 10th	Day	18% 13% 4 8% 5% 5% 5% 3 5% 7% 28%	2280
	11th to 20th	Day	19% 9% 3 8% 6% 5% 5% 4 6% 8% 28%	2618
	21st to end	Day	17% 14% 5% 10% 5% 5% 3 3 5% 7% 25%	3476
January	1st to 10th	Night	13% 17% 6% 13% 8% 6% 6% 4 5% 6% 15%	6787
	11th to 20th	Night	12% 14% 7% 12% 8% 6% 5% 4 6% 5% 22%	6315
	21st to end	Night	6% 11% 4 9% 5% 6% 6% 5% 6% 8% 33%	6996
February	1st to 10th	Night	12% 14% 4 9% 6% 6% 5% 4 5% 7% 28%	2616
	11th to 20th	Night	13% 14% 6% 10% 7% 6% 5% 4 5% 6% 24%	2515
	21st to end	Night	13% 13% 3 9% 6% 5% 5% 4 4 4 34%	1885
March	1st to 10th	Night	18% 12% 3 8% 5% 4 6% 4 5% 6% 28%	3670
	11th to 20th	Night	15% 17% 6% 11% 6% 5% 5% 3 4 5% 22%	3479
	21st to end	Night	26% 13% 3 7% 3 3 3 2 4 7% 28%	3816
April	1st to 10th	Night	22% 12% 3 7% 5% 5% 4 3 5% 4 32%	1900
	11th to 20th	Night	20% 9% 2 7% 5% 4 4 4 5% 7% 34%	1688
	21st to end	Night	24% 10% 3 6% 4 5% 4 3 5% 5% 32%	1710
May	1st to 10th	Night	20% 9% 2 6% 4 4 4 4 6% 7% 33%	2834
	11th to 20th	Night	21% 8% 3 7% 5% 5% 5% 4 5% 6% 31%	2608
	21st to end	Night	15% 6% 2 6% 4 4 5% 4 8% 7% 39%	2401
June	1st to 10th	Night	24% 8% 3 6% 4 3 5% 4 4 7% 32%	1330
	11th to 20th	Night	17% 6% 1 5% 5% 4 4 4 8% 8% 37%	1330
	21st to end	Night	23% 8% 4 7% 6% 4 4 3 5% 5% 31%	1330
July	1st to 10th	Night	12% 7% 2 7% 6% 5% 4 4 6% 9% 38%	2210
	11th to 20th	Night	19% 5% 2 6% 4 4 5% 5% 6% 7% 37%	2289
	21st to end	Night	13% 7% 2 6% 4 5% 4 4 6% 8% 42%	2739
August	1st to 10th	Night	19% 7% 3 7% 5% 5% 6% 4 7% 6% 31%	2781
	11th to 20th	Night	13% 6% 3 9% 6% 5% 5% 5% 7% 9% 33%	2782
	21st to end	Night	17% 5% 3 6% 3 4 3 3 4 6% 45%	3124
September	1st to 10th	Night	15% 5% 2 6% 4 4 4 3 6% 8% 44%	1920
	11th to 20th	Night	16% 6% 2 5% 4 4 3 4 6% 6% 45%	2090
	21st to end	Night	17% 5% 2 5% 4 3 4 4 5% 6% 45%	2090
October	1st to 10th	Night	19% 6% 3 5% 4 3 4 3 4 6% 42%	2190
	11th to 20th	Night	20% 9% 3 6% 4 4 5% 3 5% 6% 35%	2294
	21st to end	Night	23% 10% 2 7% 5% 4 4 4 5% 6% 32%	2717
November	1st to 10th	Night	20% 9% 3 5% 6% 4 4 4 5% 6% 33%	2550
	11th to 20th	Night	20% 10% 4 7% 4 4 4 4 5% 6% 31%	2800
	21st to end	Night	21% 11% 4 9% 6% 5% 5% 4 5% 6% 25%	2800
December	1st to 10th	Night	15% 12% 5% 11% 7% 5% 5% 4 6% 6% 24%	4910
	11th to 20th	Night	22% 11% 3 7% 5% 4 4 3 4 7% 30%	5591
	21st to end	Night	18% 13% 4 10% 5% 4 4 4 5% 7% 24%	7502

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	70% 2 10% 14% 4	3175
	11th to 20th	Day	62% 2 11% 20% 5%	3600
	21st to end	Day	49% 3 13% 17% 18%	3960
February	1st to 10th	Day	56% 5% 11% 17% 10% 1	1782
	11th to 20th	Day	59% 4 12% 18% 7% 1	1776
	21st to end	Day	51% 5% 11% 23% 9% 2	1570
March	1st to 10th	Day	57% 3 12% 15% 11% 3	3173
	11th to 20th	Day	65% 3 11% 13% 6% 1	3480
	21st to end	Day	60% 2 6% 20% 10% 2	3816
April	1st to 10th	Day	56% 4 10% 19% 9% 2	2276
	11th to 20th	Day	48% 3 11% 24% 12% 2	2442
	21st to end	Day	54% 3 8% 20% 12% 3	2470
May	1st to 10th	Day	53% 2 11% 24% 9% 1	4120
	11th to 20th	Day	53% 2 17% 20% 8% 1	4322
	21st to end	Day	50% 5% 12% 20% 12% 1	5185
June	1st to 10th	Day	52% 5% 15% 17% 10% 1	2850
	11th to 20th	Day	49% 4 14% 20% 11% 2	2850
	21st to end	Day	58% 5% 12% 16% 8%	2850
July	1st to 10th	Day	50% 3 18% 20% 8%	4685
	11th to 20th	Day	47% 3 17% 27% 5%	4595
	21st to end	Day	44% 4 18% 26% 8%	4661
August	1st to 10th	Day	49% 5% 18% 22% 7%	4102
	11th to 20th	Day	52% 4 17% 22% 4	4084
	21st to end	Day	46% 3 15% 25% 11%	4532
September	1st to 10th	Day	43% 4 15% 26% 13%	2257
	11th to 20th	Day	39% 3 14% 29% 15%	2090
	21st to end	Day	43% 5% 12% 29% 11%	2090
October	1st to 10th	Day	51% 2 13% 28% 5%	3301
	11th to 20th	Day	51% 2 12% 28% 7%	3109
	21st to end	Day	50% 3 15% 21% 12%	3081
November	1st to 10th	Day	55% 3 12% 22% 8%	1746
	11th to 20th	Day	57% 5% 11% 18% 8% 1	1600
	21st to end	Day	61% 3 16% 18% 3	1598
December	1st to 10th	Day	57% 2 18% 13% 9%	2280
	11th to 20th	Day	56% 3 10% 20% 9% 2	2618
	21st to end	Day	62% 3 11% 13% 10% 1	3476
January	1st to 10th	Night	72% 2 12% 11% 3	6787
	11th to 20th	Night	65% 3 10% 17% 5%	6360
	21st to end	Night	50% 3 10% 21% 16% 1	6996
February	1st to 10th	Night	56% 4 11% 16% 11% 1	2616
	11th to 20th	Night	62% 4 9% 16% 8% 1	2518
	21st to end	Night	54% 3 9% 20% 12% 1	1885
March	1st to 10th	Night	57% 4 10% 21% 8% 1	3679
	11th to 20th	Night	66% 2 9% 15% 7% 1	3480
	21st to end	Night	59% 2 5% 21% 11% 2	3816
April	1st to 10th	Night	55% 4 8% 18% 12% 4	1900
	11th to 20th	Night	50% 3 9% 21% 15% 2	1688
	21st to end	Night	55% 3 7% 18% 16% 2	1710
May	1st to 10th	Night	50% 4 14% 21% 11% 1	2840
	11th to 20th	Night	54% 2 12% 24% 7% 1	2609
	21st to end	Night	43% 4 13% 25% 14%	2402
June	1st to 10th	Night	52% 4 11% 22% 9% 1	1330
	11th to 20th	Night	43% 5% 16% 22% 12% 2	1330
	21st to end	Night	55% 5% 12% 17% 9% 1	1330
July	1st to 10th	Night	44% 3 22% 22% 9%	2175
	11th to 20th	Night	47% 4 17% 26% 6%	2247
	21st to end	Night	41% 4 21% 25% 8%	2651
August	1st to 10th	Night	53% 4 16% 23% 5%	2771
	11th to 20th	Night	48% 5% 23% 17% 7%	2809
	21st to end	Night	42% 3 15% 25% 14%	3124
September	1st to 10th	Night	40% 4 14% 30% 12% 1	1920
	11th to 20th	Night	40% 4 14% 28% 13%	2090
	21st to end	Night	41% 5% 13% 27% 14% 1	2090
October	1st to 10th	Night	50% 2 11% 29% 8%	3658
	11th to 20th	Night	49% 2 12% 30% 7%	3805
	21st to end	Night	45% 3 19% 21% 12%	4467
November	1st to 10th	Night	53% 4 14% 22% 7%	2550
	11th to 20th	Night	55% 4 13% 18% 10% 1	2800
	21st to end	Night	61% 5% 14% 14% 5% 1	2800
December	1st to 10th	Night	64% 2 11% 18% 4	4910
	11th to 20th	Night	58% 2 9% 21% 9% 1	5592
	21st to end	Night	61% 2 9% 19% 8% 1	7502

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	22% 18% 30% 24% 7%	200
	11th to 20th	Day	27% 16% 28% 17% 12% 1	200
	21st to end	Day	17% 15% 35% 19% 11% 4	220
February	1st to 10th	Day	22% 13% 31% 26% 7% 1	382
	11th to 20th	Day	18% 17% 39% 22% 4	403
	21st to end	Day	17% 18% 34% 24% 7%	382
March	1st to 10th	Day	25% 13% 32% 24% 6%	460
	11th to 20th	Day	22% 16% 28% 23% 10% 1	460
	21st to end	Day	25% 15% 27% 22% 9% 2	506
April	1st to 10th	Day	28% 16% 29% 18% 8% 1	460
	11th to 20th	Day	21% 13% 30% 23% 10% 2	452
	21st to end	Day	31% 13% 24% 22% 8% 2	460
May	1st to 10th	Day	26% 16% 26% 23% 8% 1	463
	11th to 20th	Day	27% 14% 26% 22% 9% 3	574
	21st to end	Day	23% 15% 32% 21% 7% 1	735
June	1st to 10th	Day	25% 15% 29% 21% 9% 2	680
	11th to 20th	Day	21% 13% 26% 24% 13% 2	680
	21st to end	Day	26% 8% 31% 23% 11% 1	680
July	1st to 10th	Day	18% 7% 33% 27% 13% 2	670
	11th to 20th	Day	16% 8% 29% 31% 15% 2	623
	21st to end	Day	17% 5% 31% 32% 13% 3	532
August	1st to 10th	Day	18% 9% 28% 28% 13% 4	486
	11th to 20th	Day	17% 8% 26% 29% 17% 3	479
	21st to end	Day	19% 12% 21% 26% 17% 6%	539
September	1st to 10th	Day	16% 12% 27% 26% 15% 4	490
	11th to 20th	Day	20% 10% 24% 25% 14% 6%	490
	21st to end	Day	21% 11% 27% 22% 12% 7%	490
October	1st to 10th	Day	19% 12% 29% 21% 14% 5%	436
	11th to 20th	Day	27% 16% 26% 17% 11% 3	390
	21st to end	Day	28% 16% 28% 19% 7% 1	429
November	1st to 10th	Day	29% 16% 27% 21% 7% 1	395
	11th to 20th	Day	26% 15% 32% 20% 7% 1	400
	21st to end	Day	29% 16% 30% 20% 5% 1	398
December	1st to 10th	Day	21% 14% 33% 18% 13% 2	200
	11th to 20th	Day	25% 17% 34% 18% 5% 2	200
	21st to end	Day	25% 16% 32% 18% 7% 2	220
January	1st to 10th	Night	21% 14% 36% 24% 5%	895
	11th to 20th	Night	25% 14% 31% 23% 7%	800
	21st to end	Night	15% 12% 39% 27% 8%	880
February	1st to 10th	Night	17% 13% 41% 23% 6% 1	800
	11th to 20th	Night	21% 15% 35% 24% 5%	783
	21st to end	Night	22% 11% 35% 27% 4 1	629
March	1st to 10th	Night	19% 10% 39% 29% 4	760
	11th to 20th	Night	22% 13% 32% 24% 8% 1	760
	21st to end	Night	23% 8% 37% 26% 6% 1	836
April	1st to 10th	Night	28% 12% 29% 26% 5%	722
	11th to 20th	Night	24% 12% 31% 26% 7%	564
	21st to end	Night	29% 10% 29% 24% 7%	570
May	1st to 10th	Night	26% 9% 30% 28% 6%	570
	11th to 20th	Night	26% 8% 30% 28% 7% 1	531
	21st to end	Night	21% 9% 34% 29% 6%	411
June	1st to 10th	Night	25% 6% 27% 34% 8% 1	380
	11th to 20th	Night	20% 3 25% 40% 12%	380
	21st to end	Night	23% 7% 27% 31% 12%	380
July	1st to 10th	Night	19% 5% 29% 35% 12%	370
	11th to 20th	Night	15% 5% 27% 40% 13%	368
	21st to end	Night	20% 4 21% 38% 16% 1	416
August	1st to 10th	Night	18% 4 20% 42% 15%	536
	11th to 20th	Night	15% 3 23% 43% 17%	562
	21st to end	Night	11% 6% 28% 37% 17% 2	627
September	1st to 10th	Night	17% 5% 32% 33% 13%	676
	11th to 20th	Night	19% 7% 24% 35% 14% 1	760
	21st to end	Night	21% 7% 26% 31% 15% 1	760
October	1st to 10th	Night	22% 7% 29% 29% 12% 1	760
	11th to 20th	Night	25% 9% 33% 25% 9%	760
	21st to end	Night	27% 11% 33% 23% 6%	836
November	1st to 10th	Night	26% 10% 33% 24% 6% 1	787
	11th to 20th	Night	23% 18% 30% 23% 6% 1	900
	21st to end	Night	27% 13% 32% 24% 4	900
December	1st to 10th	Night	30% 8% 34% 22% 5% 1	900
	11th to 20th	Night	25% 15% 31% 24% 4	900
	21st to end	Night	27% 15% 30% 22% 5% 1	990

Page generated at 2025-02-18 03:26:32. Version ac07

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