Berry Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Berry Creek clear sky chart from 2005-11-06 to 2026-01-02.

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	8% 8% 3 8% 5% 5% 5% 4 6% 8% 38%	131562
	Night	7% 9% 4 10% 6% 6% 6% 5% 6% 8% 35%	128510
Transparency	Day	42% 7% 16% 25% 10% 1	131258
	Night	44% 7% 16% 23% 10% 1	128393
Seeing	Day	11% 8% 26% 31% 19% 5%	16982
	Night	11% 6% 30% 36% 15% 2	26170

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% 11% 5% 14% 8% 7% 6% 5% 5% 7% 27%	3186
	11th to 20th	Day	3 11% 5% 10% 8% 7% 6% 7% 8% 10% 27%	3159
	21st to end	Day	3 10% 5% 11% 6% 4 5% 5% 6% 9% 37%	3750
February	1st to 10th	Day	6% 15% 5% 13% 7% 7% 6% 4 7% 8% 24%	1665
	11th to 20th	Day	5% 13% 5% 11% 7% 6% 6% 5% 7% 7% 27%	1755
	21st to end	Day	4 12% 4 11% 8% 7% 7% 6% 8% 11% 23%	1490
March	1st to 10th	Day	3 9% 4 11% 8% 7% 6% 4 6% 8% 33%	4639
	11th to 20th	Day	5% 12% 5% 12% 7% 5% 4 3 5% 7% 34%	4999
	21st to end	Day	8% 14% 6% 13% 7% 5% 5% 4 6% 7% 25%	5486
April	1st to 10th	Day	8% 12% 4 9% 6% 5% 5% 4 6% 8% 33%	2480
	11th to 20th	Day	10% 12% 5% 9% 5% 4 5% 4 6% 8% 31%	2570
	21st to end	Day	12% 10% 4 8% 6% 5% 5% 4 6% 9% 31%	2600
May	1st to 10th	Day	13% 9% 3 7% 4 4 5% 4 6% 6% 39%	6328
	11th to 20th	Day	13% 10% 4 9% 6% 6% 5% 5% 6% 8% 27%	6734
	21st to end	Day	11% 7% 3 8% 5% 5% 5% 4 6% 7% 40%	7405
June	1st to 10th	Day	15% 7% 2 6% 6% 5% 5% 5% 7% 9% 33%	3000
	11th to 20th	Day	18% 8% 3 8% 5% 5% 6% 4 6% 9% 28%	3000
	21st to end	Day	9% 5% 2 6% 6% 6% 6% 6% 7% 8% 40%	3000
July	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 7% 8% 48%	6780
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 4 7% 9% 43%	6780
	21st to end	Day	7% 4 2 5% 4 4 5% 4 6% 9% 50%	7376
August	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 4 6% 8% 45%	4621
	11th to 20th	Day	6% 4 2 6% 4 4 5% 5% 7% 10% 48%	4158
	21st to end	Day	8% 4 2 5% 4 4 4 4 6% 9% 50%	4664
September	1st to 10th	Day	10% 6% 2 5% 3 4 4 4 5% 8% 48%	2513
	11th to 20th	Day	15% 6% 2 5% 4 4 4 3 6% 7% 44%	2220
	21st to end	Day	7% 6% 2 6% 4 4 5% 3 5% 9% 49%	2200
October	1st to 10th	Day	6% 7% 3 7% 5% 5% 5% 4 5% 7% 46%	3313
	11th to 20th	Day	5% 7% 3 7% 5% 5% 6% 5% 7% 9% 42%	3143
	21st to end	Day	6% 8% 3 7% 5% 5% 5% 4 6% 7% 42%	3113
November	1st to 10th	Day	8% 15% 6% 10% 7% 6% 5% 4 6% 7% 28%	1648
	11th to 20th	Day	4 13% 5% 11% 8% 6% 5% 3 5% 8% 33%	1670
	21st to end	Day	5% 10% 5% 13% 8% 6% 5% 5% 6% 7% 30%	1470
December	1st to 10th	Day	10% 15% 4 12% 6% 6% 6% 5% 6% 8% 24%	2360
	11th to 20th	Day	5% 12% 6% 14% 7% 8% 6% 5% 7% 6% 22%	2712
	21st to end	Day	4 7% 3 10% 8% 5% 5% 4 6% 7% 41%	3575
January	1st to 10th	Night	3 10% 5% 13% 9% 8% 6% 6% 7% 8% 25%	6782
	11th to 20th	Night	3 8% 4 12% 8% 6% 6% 5% 6% 8% 34%	6739
	21st to end	Night	4 9% 4 13% 6% 6% 6% 4 6% 7% 36%	7251
February	1st to 10th	Night	6% 10% 4 11% 8% 5% 5% 5% 8% 8% 28%	2735
	11th to 20th	Night	5% 12% 4 11% 8% 6% 6% 5% 8% 8% 26%	2532
	21st to end	Night	5% 9% 3 10% 7% 7% 6% 5% 8% 10% 31%	2135
March	1st to 10th	Night	2 9% 4 11% 8% 7% 7% 6% 7% 10% 28%	5255
	11th to 20th	Night	4 10% 4 10% 7% 6% 6% 5% 7% 9% 32%	5000
	21st to end	Night	7% 13% 6% 17% 8% 7% 5% 4 6% 6% 20%	5489
April	1st to 10th	Night	7% 11% 4 9% 6% 6% 5% 4 6% 7% 34%	1917
	11th to 20th	Night	9% 10% 4 10% 7% 5% 4 5% 7% 8% 30%	1781
	21st to end	Night	10% 10% 4 9% 5% 5% 5% 4 7% 8% 34%	1800
May	1st to 10th	Night	15% 10% 3 7% 6% 5% 5% 3 5% 6% 34%	3647
	11th to 20th	Night	11% 8% 3 9% 6% 6% 7% 5% 8% 9% 28%	3159
	21st to end	Night	13% 8% 3 9% 5% 5% 5% 4 5% 7% 35%	3470
June	1st to 10th	Night	14% 8% 3 8% 5% 5% 6% 5% 7% 8% 32%	1400
	11th to 20th	Night	14% 8% 3 6% 6% 6% 6% 5% 6% 9% 31%	1400
	21st to end	Night	11% 5% 2 5% 5% 4 5% 4 6% 8% 44%	1400
July	1st to 10th	Night	6% 4 2 6% 4 5% 5% 4 7% 9% 48%	3180
	11th to 20th	Night	9% 5% 2 5% 5% 5% 6% 4 7% 10% 43%	3180
	21st to end	Night	8% 4 2 6% 4 4 5% 4 6% 9% 48%	3467
August	1st to 10th	Night	10% 7% 2 6% 4 4 4 4 6% 8% 44%	2528
	11th to 20th	Night	6% 4 2 7% 5% 5% 5% 4 6% 10% 46%	2901
	21st to end	Night	8% 5% 2 6% 4 4 4 4 6% 9% 48%	3245
September	1st to 10th	Night	8% 5% 2 7% 4 5% 5% 3 6% 8% 48%	1887
	11th to 20th	Night	13% 7% 1 4 4 4 4 3 5% 7% 46%	2178
	21st to end	Night	7% 6% 2 6% 3 4 5% 4 6% 8% 48%	2200
October	1st to 10th	Night	7% 7% 2 7% 4 5% 5% 5% 6% 9% 42%	3878
	11th to 20th	Night	5% 5% 2 7% 5% 4 5% 5% 6% 9% 46%	3992
	21st to end	Night	6% 9% 4 8% 5% 5% 6% 5% 8% 9% 36%	4654
November	1st to 10th	Night	9% 13% 5% 8% 7% 5% 4 4 6% 7% 32%	2870
	11th to 20th	Night	5% 10% 5% 10% 6% 6% 7% 5% 6% 7% 32%	2945
	21st to end	Night	5% 11% 4 11% 7% 6% 6% 4 7% 9% 30%	3150
December	1st to 10th	Night	10% 13% 5% 13% 7% 6% 6% 4 6% 8% 23%	5040
	11th to 20th	Night	5% 13% 5% 14% 8% 7% 5% 4 7% 8% 22%	5700
	21st to end	Night	3 6% 3 9% 7% 6% 6% 4 6% 8% 42%	7623

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	56% 6% 10% 20% 7%	3186
	11th to 20th	Day	48% 6% 13% 13% 19% 1	3180
	21st to end	Day	41% 7% 22% 24% 6%	3750
February	1st to 10th	Day	54% 6% 14% 16% 8% 1	1665
	11th to 20th	Day	52% 7% 14% 15% 11% 1	1764
	21st to end	Day	52% 6% 14% 18% 10%	1490
March	1st to 10th	Day	45% 6% 19% 20% 9%	4639
	11th to 20th	Day	47% 7% 15% 19% 11%	5000
	21st to end	Day	54% 8% 13% 19% 6%	5486
April	1st to 10th	Day	46% 7% 17% 20% 10%	2480
	11th to 20th	Day	49% 6% 13% 23% 9% 1	2570
	21st to end	Day	47% 9% 15% 21% 7% 2	2600
May	1st to 10th	Day	43% 6% 10% 24% 13% 4	6328
	11th to 20th	Day	50% 9% 12% 22% 7%	6738
	21st to end	Day	39% 8% 16% 24% 11% 2	7406
June	1st to 10th	Day	43% 8% 16% 23% 10% 1	3000
	11th to 20th	Day	52% 8% 16% 19% 6% 1	3000
	21st to end	Day	36% 10% 22% 23% 7% 1	3000
July	1st to 10th	Day	30% 8% 17% 31% 13% 1	6706
	11th to 20th	Day	36% 7% 17% 27% 12%	6699
	21st to end	Day	28% 7% 17% 30% 15% 2	7169
August	1st to 10th	Day	34% 9% 17% 31% 9%	4603
	11th to 20th	Day	28% 8% 23% 32% 8% 1	4197
	21st to end	Day	28% 6% 21% 34% 10% 1	4663
September	1st to 10th	Day	33% 7% 17% 27% 12% 5%	2513
	11th to 20th	Day	38% 5% 16% 30% 9% 1	2220
	21st to end	Day	33% 7% 16% 30% 12% 3	2200
October	1st to 10th	Day	36% 5% 19% 30% 10%	3313
	11th to 20th	Day	36% 6% 16% 31% 9% 1	3143
	21st to end	Day	39% 6% 13% 35% 7%	3113
November	1st to 10th	Day	54% 6% 13% 19% 6% 1	1648
	11th to 20th	Day	50% 7% 15% 21% 6% 1	1670
	21st to end	Day	50% 7% 17% 19% 6%	1470
December	1st to 10th	Day	57% 8% 17% 13% 4 1	2360
	11th to 20th	Day	58% 7% 16% 16% 3	2714
	21st to end	Day	41% 5% 9% 28% 14% 3	3575
January	1st to 10th	Night	53% 7% 15% 17% 6% 1	6782
	11th to 20th	Night	47% 6% 14% 16% 16% 1	6780
	21st to end	Night	45% 7% 16% 26% 6%	7251
February	1st to 10th	Night	48% 7% 14% 20% 11%	2735
	11th to 20th	Night	52% 7% 13% 17% 10% 1	2533
	21st to end	Night	44% 8% 14% 23% 10% 1	2135
March	1st to 10th	Night	46% 8% 19% 20% 7%	5255
	11th to 20th	Night	44% 8% 16% 24% 7%	5000
	21st to end	Night	60% 8% 11% 15% 7%	5489
April	1st to 10th	Night	45% 7% 15% 20% 12% 1	1917
	11th to 20th	Night	48% 7% 11% 22% 11% 1	1781
	21st to end	Night	43% 8% 13% 23% 11% 2	1800
May	1st to 10th	Night	48% 6% 8% 23% 13% 2	3646
	11th to 20th	Night	43% 11% 16% 21% 7% 1	3159
	21st to end	Night	44% 9% 15% 23% 8% 1	3470
June	1st to 10th	Night	47% 8% 14% 21% 10% 2	1400
	11th to 20th	Night	46% 9% 17% 19% 9% 1	1400
	21st to end	Night	34% 9% 21% 26% 8% 1	1400
July	1st to 10th	Night	30% 9% 22% 22% 16% 1	3145
	11th to 20th	Night	34% 8% 20% 30% 8% 2	3138
	21st to end	Night	31% 8% 20% 27% 13% 2	3369
August	1st to 10th	Night	34% 8% 18% 32% 8% 1	2521
	11th to 20th	Night	32% 7% 18% 36% 6% 1	2928
	21st to end	Night	32% 6% 16% 33% 12% 1	3245
September	1st to 10th	Night	32% 8% 17% 22% 15% 7%	1887
	11th to 20th	Night	36% 7% 14% 29% 12% 3	2178
	21st to end	Night	32% 7% 15% 28% 16% 2	2200
October	1st to 10th	Night	36% 5% 20% 27% 10% 1	3878
	11th to 20th	Night	32% 5% 17% 34% 11% 1	3992
	21st to end	Night	40% 7% 16% 32% 5%	4654
November	1st to 10th	Night	50% 7% 13% 20% 9% 1	2870
	11th to 20th	Night	47% 8% 16% 19% 9% 1	2945
	21st to end	Night	49% 7% 17% 19% 7% 1	3150
December	1st to 10th	Night	59% 6% 15% 14% 5% 1	5040
	11th to 20th	Night	57% 7% 19% 12% 4	5697
	21st to end	Night	40% 6% 12% 23% 17% 3	7623

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	5% 5% 35% 30% 19% 5%	202
	11th to 20th	Day	7% 9% 33% 35% 13% 5%	200
	21st to end	Day	9% 10% 37% 26% 13% 5%	220
February	1st to 10th	Day	13% 9% 30% 33% 10% 4	233
	11th to 20th	Day	11% 6% 29% 39% 11% 3	300
	21st to end	Day	7% 6% 34% 28% 23% 4	254
March	1st to 10th	Day	8% 9% 32% 32% 16% 2	500
	11th to 20th	Day	9% 7% 34% 31% 14% 5%	500
	21st to end	Day	12% 8% 30% 32% 16% 3	550
April	1st to 10th	Day	11% 13% 30% 31% 10% 5%	500
	11th to 20th	Day	11% 10% 35% 29% 11% 3	492
	21st to end	Day	17% 9% 27% 30% 13% 4	500
May	1st to 10th	Day	15% 11% 23% 28% 19% 4	678
	11th to 20th	Day	13% 8% 22% 31% 22% 6%	725
	21st to end	Day	16% 7% 20% 27% 21% 9%	789
June	1st to 10th	Day	16% 8% 23% 33% 15% 4	730
	11th to 20th	Day	17% 11% 25% 27% 15% 5%	730
	21st to end	Day	10% 5% 22% 31% 23% 8%	730
July	1st to 10th	Day	8% 4 20% 34% 28% 6%	721
	11th to 20th	Day	12% 7% 20% 31% 22% 8%	718
	21st to end	Day	5% 5% 18% 32% 29% 11%	794
August	1st to 10th	Day	10% 4 21% 30% 24% 10%	617
	11th to 20th	Day	8% 5% 22% 33% 26% 6%	517
	21st to end	Day	8% 7% 21% 28% 27% 8%	583
September	1st to 10th	Day	12% 8% 26% 29% 21% 5%	530
	11th to 20th	Day	16% 5% 23% 32% 18% 5%	530
	21st to end	Day	12% 12% 29% 28% 16% 3	530
October	1st to 10th	Day	14% 7% 28% 30% 17% 5%	360
	11th to 20th	Day	10% 11% 31% 31% 14% 3	330
	21st to end	Day	10% 11% 39% 27% 10% 2	363
November	1st to 10th	Day	14% 8% 32% 31% 12% 2	330
	11th to 20th	Day	11% 10% 37% 27% 13% 1	324
	21st to end	Day	9% 7% 31% 32% 16% 5%	220
December	1st to 10th	Day	10% 8% 35% 30% 14% 2	220
	11th to 20th	Day	8% 13% 34% 31% 11% 2	220
	21st to end	Day	10% 9% 24% 33% 18% 7%	242
January	1st to 10th	Night	8% 7% 36% 34% 14% 1	1006
	11th to 20th	Night	9% 10% 34% 34% 12% 1	1000
	21st to end	Night	11% 10% 34% 31% 12% 2	1010
February	1st to 10th	Night	11% 9% 25% 36% 16% 3	800
	11th to 20th	Night	10% 5% 36% 34% 14% 1	784
	21st to end	Night	6% 4 25% 39% 20% 5%	660
March	1st to 10th	Night	7% 5% 31% 38% 16% 3	800
	11th to 20th	Night	10% 6% 31% 38% 12% 3	800
	21st to end	Night	14% 6% 28% 34% 14% 4	880
April	1st to 10th	Night	11% 7% 31% 32% 15% 3	655
	11th to 20th	Night	14% 7% 35% 32% 11% 1	593
	21st to end	Night	14% 7% 24% 41% 13% 1	600
May	1st to 10th	Night	16% 7% 24% 36% 15% 2	582
	11th to 20th	Night	9% 6% 25% 38% 20% 2	394
	21st to end	Night	18% 5% 21% 30% 23% 2	433
June	1st to 10th	Night	17% 8% 28% 33% 13% 2	400
	11th to 20th	Night	17% 7% 26% 32% 17% 2	400
	21st to end	Night	12% 3 24% 35% 25% 2	400
July	1st to 10th	Night	11% 3 23% 43% 20% 1	390
	11th to 20th	Night	11% 3 25% 41% 20% 1	388
	21st to end	Night	5% 5% 21% 40% 27% 3	438
August	1st to 10th	Night	7% 4 23% 36% 26% 4	435
	11th to 20th	Night	9% 6% 20% 42% 22% 1	594
	21st to end	Night	8% 5% 23% 39% 24% 1	660
September	1st to 10th	Night	10% 4 25% 40% 19% 2	600
	11th to 20th	Night	15% 3 21% 41% 19% 1	778
	21st to end	Night	9% 6% 30% 39% 15% 1	800
October	1st to 10th	Night	12% 5% 28% 38% 15% 2	800
	11th to 20th	Night	10% 5% 35% 35% 13% 2	800
	21st to end	Night	11% 9% 33% 37% 10% 1	910
November	1st to 10th	Night	15% 8% 32% 35% 9% 1	1025
	11th to 20th	Night	9% 8% 38% 33% 10% 2	1050
	21st to end	Night	8% 6% 35% 37% 13% 1	1050
December	1st to 10th	Night	12% 7% 34% 31% 14% 3	1050
	11th to 20th	Night	9% 9% 37% 32% 11% 2	1050
	21st to end	Night	10% 4 34% 34% 15% 3	1155

Page generated at 2025-12-29 23:14:05. Version ac07

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