Brooks Camp Developed Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brooks Camp Developed Area clear sky chart from 2005-11-06 to 2025-11-18.

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	19% 15% 5% 11% 6% 6% 5% 4 5% 6% 18%	131451
	Night	15% 16% 5% 12% 7% 6% 5% 4 5% 6% 19%	127797
Transparency	Day	64% 10% 12% 10% 4 1	131119
	Night	60% 10% 12% 11% 6% 1	127711
Seeing	Day	25% 13% 23% 22% 13% 4	20488
	Night	23% 12% 22% 25% 16% 3	24390

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	7% 14% 4 10% 7% 7% 8% 7% 9% 8% 21%	2279
	11th to 20th	Day	7% 13% 5% 15% 6% 7% 6% 5% 6% 7% 24%	2526
	21st to end	Day	11% 12% 3 8% 6% 4 5% 5% 6% 9% 31%	3476
February	1st to 10th	Day	10% 14% 4 10% 8% 7% 6% 4 7% 8% 21%	1406
	11th to 20th	Day	12% 20% 5% 14% 7% 6% 8% 5% 6% 5% 14%	1662
	21st to end	Day	12% 16% 5% 12% 9% 6% 6% 4 5% 5% 21%	1485
March	1st to 10th	Day	7% 18% 5% 14% 8% 8% 7% 3 4 5% 21%	4285
	11th to 20th	Day	4 7% 3 12% 9% 11% 10% 4 5% 7% 27%	4980
	21st to end	Day	10% 21% 7% 17% 6% 6% 5% 3 5% 4 17%	5547
April	1st to 10th	Day	11% 19% 7% 12% 6% 6% 5% 3 5% 5% 21%	2578
	11th to 20th	Day	12% 16% 5% 11% 8% 5% 4 3 5% 5% 26%	2572
	21st to end	Day	11% 17% 5% 11% 6% 4 5% 4 6% 7% 25%	2850
May	1st to 10th	Day	15% 22% 6% 13% 6% 5% 4 3 4 4 18%	6820
	11th to 20th	Day	17% 18% 7% 12% 6% 5% 5% 3 5% 5% 16%	7025
	21st to end	Day	17% 18% 5% 11% 6% 5% 4 3 5% 6% 19%	8177
June	1st to 10th	Day	17% 16% 4 11% 6% 5% 5% 4 5% 6% 20%	3400
	11th to 20th	Day	20% 14% 4 9% 5% 5% 6% 4 5% 6% 23%	3400
	21st to end	Day	26% 13% 4 9% 6% 6% 4 5% 5% 6% 16%	3400
July	1st to 10th	Day	35% 13% 4 8% 4 4 4 3 4 5% 15%	7720
	11th to 20th	Day	31% 13% 4 10% 5% 4 4 3 4 5% 16%	7720
	21st to end	Day	27% 14% 5% 10% 6% 5% 4 3 4 6% 17%	7580
August	1st to 10th	Day	29% 12% 4 11% 6% 5% 5% 4 6% 6% 12%	4887
	11th to 20th	Day	28% 16% 6% 12% 6% 4 4 3 4 4 12%	4671
	21st to end	Day	33% 15% 4 10% 7% 5% 5% 4 5% 4 8%	4675
September	1st to 10th	Day	32% 14% 5% 11% 5% 5% 4 3 4 4 12%	2551
	11th to 20th	Day	29% 13% 5% 10% 5% 5% 5% 4 4 5% 15%	2311
	21st to end	Day	24% 16% 4 9% 5% 5% 4 3 4 5% 21%	2168
October	1st to 10th	Day	18% 15% 5% 10% 7% 6% 6% 5% 6% 5% 18%	3260
	11th to 20th	Day	10% 13% 5% 10% 5% 6% 5% 4 5% 6% 31%	2975
	21st to end	Day	14% 15% 7% 13% 7% 7% 6% 4 6% 5% 16%	2831
November	1st to 10th	Day	16% 19% 7% 14% 7% 5% 5% 3 4 6% 16%	1572
	11th to 20th	Day	12% 14% 6% 11% 7% 10% 7% 4 6% 6% 17%	1313
	21st to end	Day	15% 17% 4 13% 9% 8% 7% 5% 6% 5% 12%	1200
December	1st to 10th	Day	16% 13% 6% 13% 8% 8% 6% 5% 5% 5% 14%	1754
	11th to 20th	Day	10% 19% 6% 14% 7% 7% 7% 5% 5% 7% 14%	1887
	21st to end	Day	8% 17% 5% 12% 8% 6% 7% 4 6% 7% 21%	2508
January	1st to 10th	Night	7% 15% 5% 13% 9% 7% 7% 6% 6% 6% 18%	7707
	11th to 20th	Night	7% 15% 5% 13% 8% 6% 5% 5% 5% 5% 25%	7405
	21st to end	Night	9% 12% 4 9% 6% 5% 5% 4 8% 9% 29%	7502
February	1st to 10th	Night	10% 16% 5% 9% 7% 6% 6% 5% 6% 7% 25%	2991
	11th to 20th	Night	14% 20% 5% 10% 7% 6% 7% 5% 5% 5% 16%	2624
	21st to end	Night	12% 16% 4 11% 6% 5% 5% 3 5% 5% 27%	2145
March	1st to 10th	Night	10% 19% 7% 17% 8% 7% 5% 3 3 4 18%	5555
	11th to 20th	Night	4 10% 5% 14% 11% 12% 7% 3 5% 7% 20%	4978
	21st to end	Night	10% 24% 10% 14% 5% 5% 4 3 4 4 17%	5384
April	1st to 10th	Night	15% 18% 6% 14% 7% 5% 4 4 5% 4 20%	1820
	11th to 20th	Night	11% 17% 6% 11% 6% 5% 5% 4 5% 6% 25%	1777
	21st to end	Night	12% 17% 4 11% 7% 5% 4 5% 4 6% 26%	1547
May	1st to 10th	Night	16% 19% 5% 10% 5% 5% 5% 4 5% 6% 21%	3160
	11th to 20th	Night	18% 16% 5% 14% 7% 6% 5% 4 5% 5% 16%	2889
	21st to end	Night	19% 18% 5% 11% 7% 5% 6% 4 6% 6% 13%	2717
June	1st to 10th	Night	21% 13% 4 12% 6% 6% 5% 3 5% 5% 21%	1000
	11th to 20th	Night	23% 12% 5% 8% 7% 4 5% 4 6% 5% 22%	1000
	21st to end	Night	25% 11% 5% 10% 5% 5% 6% 4 6% 7% 17%	1000
July	1st to 10th	Night	38% 12% 4 8% 4 3 4 3 3 4 17%	2280
	11th to 20th	Night	29% 14% 5% 12% 6% 4 5% 4 4 4 14%	2280
	21st to end	Night	32% 10% 3 9% 6% 5% 4 4 5% 5% 18%	3287
August	1st to 10th	Night	32% 14% 5% 9% 6% 4 5% 3 4 4 14%	2273
	11th to 20th	Night	34% 16% 5% 10% 5% 5% 4 3 4 4 11%	2385
	21st to end	Night	34% 18% 5% 10% 6% 4 5% 3 3 3 9%	3223
September	1st to 10th	Night	33% 15% 5% 11% 5% 3 4 3 4 4 14%	1849
	11th to 20th	Night	28% 13% 5% 9% 5% 5% 5% 4 5% 5% 17%	2086
	21st to end	Night	28% 13% 4 8% 6% 3 4 3 4 5% 23%	2231
October	1st to 10th	Night	19% 14% 4 8% 5% 5% 5% 4 7% 7% 22%	3920
	11th to 20th	Night	12% 14% 4 9% 6% 5% 5% 5% 6% 7% 29%	4165
	21st to end	Night	20% 16% 5% 9% 6% 6% 5% 4 6% 5% 18%	4970
November	1st to 10th	Night	17% 17% 5% 15% 7% 5% 3 3 5% 4 19%	2944
	11th to 20th	Night	11% 14% 4 10% 8% 8% 8% 3 6% 6% 20%	3242
	21st to end	Night	14% 16% 5% 11% 7% 8% 7% 5% 6% 7% 15%	3200
December	1st to 10th	Night	13% 18% 5% 13% 7% 8% 7% 5% 6% 5% 14%	5428
	11th to 20th	Night	9% 18% 6% 15% 8% 7% 6% 4 6% 7% 14%	6341
	21st to end	Night	7% 16% 6% 13% 8% 6% 7% 5% 7% 7% 19%	8492

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	46% 11% 17% 13% 11% 2	2279
	11th to 20th	Day	48% 13% 11% 16% 11% 1	2542
	21st to end	Day	43% 9% 7% 12% 21% 8%	3476
February	1st to 10th	Day	54% 11% 12% 11% 8% 5%	1406
	11th to 20th	Day	69% 8% 10% 9% 4 1	1668
	21st to end	Day	62% 11% 10% 12% 6%	1485
March	1st to 10th	Day	60% 9% 8% 11% 12% 1	4285
	11th to 20th	Day	50% 10% 12% 14% 13% 1	4980
	21st to end	Day	67% 9% 10% 10% 4 1	5547
April	1st to 10th	Day	64% 9% 12% 11% 4 1	2578
	11th to 20th	Day	60% 9% 13% 13% 6%	2572
	21st to end	Day	58% 11% 13% 14% 4 1	2850
May	1st to 10th	Day	67% 8% 8% 14% 4	6820
	11th to 20th	Day	65% 11% 13% 9% 2	7028
	21st to end	Day	62% 10% 16% 11% 1	8178
June	1st to 10th	Day	63% 12% 14% 10% 1	3400
	11th to 20th	Day	62% 11% 15% 10% 2	3400
	21st to end	Day	68% 13% 16% 3	3400
July	1st to 10th	Day	71% 9% 16% 5%	7636
	11th to 20th	Day	68% 9% 15% 8%	7627
	21st to end	Day	68% 10% 15% 7%	7369
August	1st to 10th	Day	69% 10% 12% 7% 1	4869
	11th to 20th	Day	73% 10% 11% 6%	4716
	21st to end	Day	78% 9% 9% 4	4674
September	1st to 10th	Day	75% 10% 7% 7% 1	2551
	11th to 20th	Day	70% 11% 9% 9% 1	2311
	21st to end	Day	67% 8% 11% 12% 1	2168
October	1st to 10th	Day	63% 9% 10% 15% 3	3260
	11th to 20th	Day	52% 12% 17% 15% 4	2975
	21st to end	Day	64% 12% 13% 8% 3	2831
November	1st to 10th	Day	68% 11% 10% 9% 2 1	1572
	11th to 20th	Day	64% 12% 11% 9% 4	1313
	21st to end	Day	65% 9% 12% 8% 6%	1200
December	1st to 10th	Day	63% 10% 12% 11% 4 1	1754
	11th to 20th	Day	63% 9% 13% 8% 6% 1	1891
	21st to end	Day	55% 10% 13% 12% 9% 2	2508
January	1st to 10th	Night	54% 10% 13% 12% 9% 1	7707
	11th to 20th	Night	51% 8% 10% 18% 12% 1	7452
	21st to end	Night	43% 9% 9% 13% 20% 7%	7502
February	1st to 10th	Night	53% 9% 11% 13% 10% 3	2991
	11th to 20th	Night	64% 10% 11% 9% 5% 1	2629
	21st to end	Night	56% 11% 12% 14% 7%	2145
March	1st to 10th	Night	65% 7% 8% 8% 11% 1	5555
	11th to 20th	Night	54% 12% 11% 12% 11% 1	4980
	21st to end	Night	67% 7% 12% 9% 4 1	5384
April	1st to 10th	Night	65% 9% 12% 9% 4 1	1820
	11th to 20th	Night	58% 10% 13% 14% 5%	1777
	21st to end	Night	56% 12% 14% 12% 6% 1	1547
May	1st to 10th	Night	61% 9% 10% 15% 6%	3157
	11th to 20th	Night	64% 11% 15% 8% 2	2890
	21st to end	Night	64% 13% 16% 7% 1	2717
June	1st to 10th	Night	62% 12% 15% 11% 1	1000
	11th to 20th	Night	61% 12% 14% 11% 2	1000
	21st to end	Night	67% 13% 15% 5%	1000
July	1st to 10th	Night	70% 8% 16% 6%	2255
	11th to 20th	Night	69% 11% 14% 6%	2250
	21st to end	Night	65% 12% 15% 8%	3194
August	1st to 10th	Night	71% 9% 13% 7%	2266
	11th to 20th	Night	76% 7% 12% 5%	2406
	21st to end	Night	79% 9% 8% 4	3223
September	1st to 10th	Night	73% 9% 10% 7% 1	1849
	11th to 20th	Night	69% 11% 12% 7% 1	2086
	21st to end	Night	65% 10% 12% 10% 3	2231
October	1st to 10th	Night	57% 11% 12% 19% 2	3920
	11th to 20th	Night	52% 13% 16% 16% 2	4165
	21st to end	Night	64% 12% 12% 8% 3	4970
November	1st to 10th	Night	67% 10% 10% 11% 3	2944
	11th to 20th	Night	60% 12% 11% 11% 5% 1	3242
	21st to end	Night	63% 10% 12% 9% 6%	3200
December	1st to 10th	Night	62% 12% 12% 8% 5% 1	5428
	11th to 20th	Night	61% 9% 14% 11% 4 1	6337
	21st to end	Night	54% 10% 13% 12% 10% 2	8492

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% 9% 19% 26% 20% 10%	300
	11th to 20th	Day	15% 12% 22% 25% 18% 8%	300
	21st to end	Day	14% 18% 27% 27% 8% 5%	330
February	1st to 10th	Day	17% 12% 25% 24% 11% 11%	300
	11th to 20th	Day	24% 17% 27% 19% 11% 1	348
	21st to end	Day	23% 18% 28% 20% 9% 2	331
March	1st to 10th	Day	19% 16% 28% 23% 13% 1	480
	11th to 20th	Day	9% 12% 30% 30% 15% 3	600
	21st to end	Day	19% 13% 26% 26% 13% 2	660
April	1st to 10th	Day	18% 16% 28% 21% 13% 4	600
	11th to 20th	Day	18% 13% 24% 26% 15% 4	595
	21st to end	Day	15% 14% 26% 26% 15% 5%	700
May	1st to 10th	Day	21% 15% 23% 23% 16% 3	703
	11th to 20th	Day	21% 13% 23% 26% 13% 4	725
	21st to end	Day	20% 12% 24% 25% 14% 5%	895
June	1st to 10th	Day	24% 11% 21% 22% 17% 4	930
	11th to 20th	Day	20% 10% 19% 27% 17% 6%	930
	21st to end	Day	26% 8% 20% 25% 16% 4	930
July	1st to 10th	Day	34% 11% 19% 19% 13% 3	916
	11th to 20th	Day	31% 11% 18% 22% 14% 4	912
	21st to end	Day	34% 10% 18% 18% 17% 4	828
August	1st to 10th	Day	38% 10% 17% 19% 13% 2	726
	11th to 20th	Day	31% 16% 22% 18% 10% 3	706
	21st to end	Day	35% 15% 19% 20% 8% 3	682
September	1st to 10th	Day	39% 12% 21% 16% 8% 3	620
	11th to 20th	Day	34% 15% 21% 17% 10% 4	620
	21st to end	Day	35% 11% 21% 18% 11% 5%	588
October	1st to 10th	Day	34% 15% 24% 16% 8% 3	420
	11th to 20th	Day	19% 12% 26% 19% 20% 4	420
	21st to end	Day	26% 15% 22% 21% 13% 3	462
November	1st to 10th	Day	25% 15% 25% 20% 12% 4	386
	11th to 20th	Day	19% 17% 29% 17% 11% 6%	315
	21st to end	Day	20% 16% 22% 23% 13% 5%	300
December	1st to 10th	Day	18% 14% 27% 19% 16% 6%	300
	11th to 20th	Day	20% 16% 24% 24% 12% 4	300
	21st to end	Day	21% 16% 22% 20% 14% 7%	330
January	1st to 10th	Night	14% 8% 22% 33% 20% 4	1000
	11th to 20th	Night	14% 14% 25% 27% 17% 3	983
	21st to end	Night	16% 13% 26% 31% 11% 3	990
February	1st to 10th	Night	14% 14% 23% 27% 16% 5%	891
	11th to 20th	Night	25% 15% 25% 24% 9% 2	688
	21st to end	Night	18% 18% 26% 23% 12% 2	578
March	1st to 10th	Night	15% 14% 28% 28% 13% 1	700
	11th to 20th	Night	10% 7% 26% 34% 20% 4	700
	21st to end	Night	17% 9% 20% 32% 17% 5%	752
April	1st to 10th	Night	18% 14% 24% 24% 16% 3	600
	11th to 20th	Night	18% 11% 21% 27% 20% 3	593
	21st to end	Night	17% 12% 23% 27% 17% 4	547
May	1st to 10th	Night	21% 7% 20% 23% 26% 2	400
	11th to 20th	Night	22% 9% 20% 28% 18% 3	394
	21st to end	Night	19% 7% 21% 28% 22% 3	433
June	1st to 10th	Night	26% 9% 18% 23% 21% 4	400
	11th to 20th	Night	25% 5% 15% 29% 24% 3	400
	21st to end	Night	27% 6% 16% 18% 30% 3	400
July	1st to 10th	Night	32% 8% 15% 22% 19% 4	390
	11th to 20th	Night	34% 7% 15% 24% 15% 5%	388
	21st to end	Night	39% 8% 14% 18% 17% 4	438
August	1st to 10th	Night	38% 10% 16% 19% 15% 2	398
	11th to 20th	Night	36% 15% 16% 19% 12% 3	458
	21st to end	Night	38% 11% 15% 19% 15% 2	660
September	1st to 10th	Night	38% 12% 17% 19% 12% 2	600
	11th to 20th	Night	32% 13% 15% 19% 18% 4	648
	21st to end	Night	35% 10% 19% 18% 15% 3	710
October	1st to 10th	Night	32% 15% 21% 18% 12% 2	710
	11th to 20th	Night	25% 13% 18% 25% 15% 4	715
	21st to end	Night	26% 14% 21% 23% 13% 3	1001
November	1st to 10th	Night	25% 13% 24% 20% 16% 3	930
	11th to 20th	Night	18% 16% 27% 25% 12% 3	935
	21st to end	Night	20% 10% 28% 26% 15% 2	900
December	1st to 10th	Night	19% 14% 27% 23% 13% 4	960
	11th to 20th	Night	19% 15% 26% 28% 10% 3	1000
	21st to end	Night	20% 14% 23% 22% 17% 4	1100

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