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 2024-11-12.

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% 6% 5% 5% 4 6% 8% 37%	105696
	Night	7% 9% 3 9% 6% 6% 5% 5% 7% 8% 36%	102061
Transparency	Day	41% 8% 16% 24% 10% 1	105437
	Night	43% 8% 16% 23% 9% 1	101966
Seeing	Day	12% 8% 26% 30% 19% 5%	15546
	Night	11% 6% 30% 36% 15% 2	24618

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% 13% 5% 12% 7% 7% 5% 5% 5% 9% 28%	2219
	11th to 20th	Day	3 10% 4 10% 7% 6% 6% 8% 10% 10% 27%	2199
	21st to end	Day	4 10% 5% 11% 6% 5% 5% 5% 6% 9% 34%	2610
February	1st to 10th	Day	6% 15% 4 12% 7% 7% 6% 4 7% 9% 25%	1581
	11th to 20th	Day	6% 13% 5% 11% 7% 6% 6% 5% 6% 7% 26%	1665
	21st to end	Day	4 12% 4 11% 8% 7% 7% 6% 8% 11% 23%	1418
March	1st to 10th	Day	4 11% 5% 12% 10% 8% 7% 4 4 6% 29%	3220
	11th to 20th	Day	6% 12% 3 9% 5% 5% 4 3 6% 9% 39%	3489
	21st to end	Day	6% 14% 6% 14% 8% 6% 5% 4 5% 5% 26%	3825
April	1st to 10th	Day	8% 13% 4 9% 6% 5% 5% 4 6% 8% 31%	2356
	11th to 20th	Day	10% 13% 5% 9% 5% 5% 5% 4 6% 8% 31%	2440
	21st to end	Day	12% 10% 3 8% 6% 5% 5% 4 6% 9% 31%	2470
May	1st to 10th	Day	17% 12% 4 9% 5% 5% 5% 4 6% 6% 28%	4419
	11th to 20th	Day	10% 9% 4 8% 6% 6% 5% 5% 7% 9% 30%	4694
	21st to end	Day	14% 9% 3 9% 6% 6% 6% 5% 7% 8% 28%	5161
June	1st to 10th	Day	15% 7% 3 6% 6% 5% 5% 5% 7% 9% 32%	2850
	11th to 20th	Day	18% 8% 3 9% 5% 5% 6% 4 6% 8% 27%	2850
	21st to end	Day	9% 5% 2 6% 6% 6% 6% 6% 7% 9% 40%	2850
July	1st to 10th	Day	6% 4 2 6% 4 4 5% 4 7% 8% 48%	4740
	11th to 20th	Day	8% 3 2 6% 4 4 5% 4 7% 10% 47%	4740
	21st to end	Day	4 3 2 4 4 4 5% 4 6% 9% 56%	5138
August	1st to 10th	Day	9% 5% 3 6% 4 5% 5% 4 6% 7% 46%	4479
	11th to 20th	Day	6% 4 2 6% 4 4 5% 4 7% 10% 48%	4028
	21st to end	Day	8% 4 2 5% 4 4 4 4 6% 9% 50%	4521
September	1st to 10th	Day	10% 6% 3 5% 3 4 4 4 5% 8% 47%	2388
	11th to 20th	Day	16% 6% 2 5% 5% 4 4 3 6% 7% 42%	2109
	21st to end	Day	8% 7% 2 6% 4 4 5% 3 5% 9% 48%	2090
October	1st to 10th	Day	6% 8% 3 7% 5% 5% 5% 4 5% 7% 46%	3212
	11th to 20th	Day	5% 7% 3 7% 5% 5% 6% 5% 7% 10% 42%	3046
	21st to end	Day	7% 8% 3 8% 5% 5% 5% 4 6% 8% 41%	3017
November	1st to 10th	Day	8% 15% 6% 10% 7% 6% 5% 4 5% 7% 27%	1568
	11th to 20th	Day	4 12% 5% 11% 8% 6% 4 4 5% 7% 33%	1520
	21st to end	Day	5% 10% 4 12% 7% 6% 5% 5% 7% 8% 32%	1330
December	1st to 10th	Day	6% 12% 4 14% 7% 8% 6% 5% 6% 8% 24%	1330
	11th to 20th	Day	4 10% 6% 14% 8% 7% 7% 5% 7% 6% 26%	1682
	21st to end	Day	5% 9% 3 9% 5% 5% 4 3 6% 8% 44%	2442
January	1st to 10th	Night	3 11% 5% 12% 8% 7% 6% 6% 8% 9% 26%	4726
	11th to 20th	Night	3 7% 4 11% 9% 7% 7% 6% 6% 8% 31%	4699
	21st to end	Night	4 10% 3 11% 6% 5% 6% 5% 6% 8% 34%	5077
February	1st to 10th	Night	6% 10% 4 11% 8% 5% 5% 5% 8% 8% 29%	2599
	11th to 20th	Night	5% 12% 4 11% 8% 6% 6% 5% 8% 8% 26%	2402
	21st to end	Night	5% 9% 3 10% 7% 7% 6% 5% 8% 9% 30%	2032
March	1st to 10th	Night	3 10% 5% 13% 10% 8% 7% 5% 6% 8% 26%	3654
	11th to 20th	Night	5% 9% 3 7% 6% 6% 6% 4 7% 9% 38%	3490
	21st to end	Night	6% 13% 6% 17% 8% 7% 6% 4 7% 7% 20%	3828
April	1st to 10th	Night	8% 11% 4 9% 6% 6% 5% 5% 6% 8% 33%	1821
	11th to 20th	Night	10% 10% 4 10% 7% 5% 4 5% 7% 8% 30%	1691
	21st to end	Night	10% 10% 4 9% 5% 4 5% 4 7% 8% 33%	1710
May	1st to 10th	Night	22% 13% 4 8% 6% 5% 4 3 5% 5% 25%	2547
	11th to 20th	Night	10% 7% 3 8% 6% 6% 7% 6% 7% 9% 32%	2199
	21st to end	Night	16% 9% 4 10% 6% 6% 6% 4 5% 7% 28%	2414
June	1st to 10th	Night	15% 8% 3 8% 5% 5% 5% 5% 7% 8% 31%	1330
	11th to 20th	Night	14% 9% 2 6% 6% 6% 6% 5% 6% 9% 31%	1330
	21st to end	Night	10% 5% 2 5% 6% 5% 5% 4 6% 8% 44%	1330
July	1st to 10th	Night	7% 5% 2 7% 5% 5% 5% 4 7% 8% 45%	2220
	11th to 20th	Night	5% 4 2 4 4 5% 6% 5% 7% 11% 47%	2220
	21st to end	Night	3 3 1 5% 4 4 5% 4 6% 9% 55%	2414
August	1st to 10th	Night	10% 7% 2 6% 4 4 4 4 6% 8% 45%	2450
	11th to 20th	Night	6% 4 2 7% 5% 5% 5% 4 6% 10% 46%	2811
	21st to end	Night	8% 5% 2 6% 4 5% 4 4 6% 9% 47%	3146
September	1st to 10th	Night	8% 5% 2 7% 4 5% 5% 3 5% 7% 48%	1792
	11th to 20th	Night	14% 8% 1 5% 4 4 4 3 5% 7% 45%	2069
	21st to end	Night	7% 6% 2 7% 4 4 5% 4 6% 8% 48%	2090
October	1st to 10th	Night	8% 7% 2 7% 4 5% 5% 4 6% 9% 42%	3759
	11th to 20th	Night	5% 5% 2 7% 5% 4 5% 5% 6% 9% 45%	3869
	21st to end	Night	6% 9% 4 8% 5% 5% 6% 5% 8% 9% 36%	4509
November	1st to 10th	Night	9% 13% 5% 8% 6% 5% 4 4 6% 7% 32%	2730
	11th to 20th	Night	5% 10% 5% 10% 6% 6% 7% 5% 6% 7% 32%	2679
	21st to end	Night	5% 11% 4 11% 7% 6% 6% 4 7% 9% 31%	2850
December	1st to 10th	Night	7% 12% 5% 12% 8% 7% 6% 4 6% 9% 26%	2850
	11th to 20th	Night	5% 10% 4 12% 8% 6% 5% 5% 7% 9% 28%	3510
	21st to end	Night	3 7% 3 8% 6% 5% 5% 4 6% 7% 45%	5214

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	52% 7% 12% 20% 9% 1	2219
	11th to 20th	Day	45% 7% 15% 15% 16% 1	2220
	21st to end	Day	44% 8% 21% 20% 7%	2610
February	1st to 10th	Day	53% 6% 15% 17% 8% 1	1581
	11th to 20th	Day	53% 8% 14% 15% 10%	1674
	21st to end	Day	53% 6% 15% 17% 9%	1418
March	1st to 10th	Day	52% 7% 16% 16% 9%	3220
	11th to 20th	Day	40% 9% 20% 20% 11%	3490
	21st to end	Day	54% 8% 14% 18% 6%	3825
April	1st to 10th	Day	47% 7% 17% 19% 9% 1	2356
	11th to 20th	Day	50% 6% 13% 22% 9%	2440
	21st to end	Day	46% 9% 15% 21% 7% 2	2470
May	1st to 10th	Day	53% 8% 12% 21% 5%	4419
	11th to 20th	Day	44% 10% 13% 22% 10%	4698
	21st to end	Day	47% 10% 18% 18% 7% 1	5162
June	1st to 10th	Day	44% 8% 17% 22% 9% 1	2850
	11th to 20th	Day	53% 8% 16% 18% 6% 1	2850
	21st to end	Day	36% 10% 22% 23% 7% 1	2850
July	1st to 10th	Day	29% 8% 18% 27% 15% 1	4666
	11th to 20th	Day	30% 8% 17% 31% 14% 1	4659
	21st to end	Day	22% 7% 17% 31% 20% 3	4976
August	1st to 10th	Day	34% 9% 16% 32% 9%	4461
	11th to 20th	Day	28% 8% 23% 32% 8% 1	4067
	21st to end	Day	29% 6% 22% 34% 9% 1	4520
September	1st to 10th	Day	34% 7% 17% 26% 12% 5%	2388
	11th to 20th	Day	40% 6% 16% 29% 8% 1	2109
	21st to end	Day	33% 7% 16% 30% 11% 3	2090
October	1st to 10th	Day	36% 5% 18% 30% 9%	3212
	11th to 20th	Day	36% 6% 16% 31% 9% 1	3046
	21st to end	Day	39% 6% 13% 34% 7%	3017
November	1st to 10th	Day	55% 6% 13% 19% 6% 1	1568
	11th to 20th	Day	50% 8% 14% 22% 6%	1520
	21st to end	Day	47% 8% 18% 20% 6%	1330
December	1st to 10th	Day	55% 8% 13% 16% 7% 1	1330
	11th to 20th	Day	53% 8% 15% 19% 4 1	1684
	21st to end	Day	37% 6% 11% 28% 15% 4	2442
January	1st to 10th	Night	50% 9% 15% 20% 5% 1	4726
	11th to 20th	Night	48% 6% 13% 18% 12% 2	4740
	21st to end	Night	44% 8% 15% 26% 7% 1	5077
February	1st to 10th	Night	48% 7% 14% 20% 11%	2599
	11th to 20th	Night	52% 7% 13% 17% 9% 1	2403
	21st to end	Night	45% 8% 14% 23% 10% 1	2032
March	1st to 10th	Night	52% 8% 15% 19% 7%	3654
	11th to 20th	Night	37% 10% 19% 24% 9% 1	3490
	21st to end	Night	58% 9% 13% 14% 6%	3828
April	1st to 10th	Night	46% 7% 15% 19% 12% 1	1821
	11th to 20th	Night	48% 7% 12% 22% 11% 1	1691
	21st to end	Night	44% 8% 14% 22% 11% 2	1710
May	1st to 10th	Night	58% 7% 9% 19% 6% 1	2547
	11th to 20th	Night	38% 13% 16% 23% 9% 1	2199
	21st to end	Night	50% 10% 14% 18% 7% 1	2414
June	1st to 10th	Night	47% 8% 14% 21% 9% 2	1330
	11th to 20th	Night	46% 9% 17% 19% 9% 1	1330
	21st to end	Night	34% 9% 21% 26% 9% 1	1330
July	1st to 10th	Night	33% 9% 20% 20% 17% 1	2185
	11th to 20th	Night	27% 9% 20% 32% 10% 2	2178
	21st to end	Night	23% 6% 17% 32% 18% 3	2337
August	1st to 10th	Night	34% 8% 18% 32% 8% 1	2443
	11th to 20th	Night	32% 7% 17% 36% 6% 1	2838
	21st to end	Night	33% 6% 16% 32% 11% 1	3146
September	1st to 10th	Night	33% 8% 17% 20% 15% 7%	1792
	11th to 20th	Night	37% 7% 14% 28% 12% 2	2069
	21st to end	Night	33% 7% 15% 27% 16% 2	2090
October	1st to 10th	Night	37% 5% 20% 27% 10% 1	3759
	11th to 20th	Night	33% 5% 17% 34% 10% 1	3869
	21st to end	Night	40% 7% 16% 31% 5%	4509
November	1st to 10th	Night	50% 7% 13% 20% 9% 1	2730
	11th to 20th	Night	47% 8% 16% 19% 9%	2679
	21st to end	Night	47% 7% 18% 20% 6% 1	2850
December	1st to 10th	Night	54% 6% 12% 19% 9% 1	2850
	11th to 20th	Night	49% 8% 21% 15% 6%	3507
	21st to end	Night	37% 6% 14% 22% 17% 4	5214

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	6% 4 35% 29% 20% 6%	180
	11th to 20th	Day	6% 8% 32% 34% 14% 5%	180
	21st to end	Day	10% 9% 34% 28% 14% 6%	198
February	1st to 10th	Day	14% 9% 30% 33% 10% 4	209
	11th to 20th	Day	13% 6% 31% 36% 11% 3	270
	21st to end	Day	7% 4 35% 26% 24% 4	230
March	1st to 10th	Day	9% 9% 33% 31% 16% 2	460
	11th to 20th	Day	9% 7% 35% 30% 13% 5%	460
	21st to end	Day	11% 9% 30% 32% 15% 3	506
April	1st to 10th	Day	11% 14% 31% 30% 10% 4	460
	11th to 20th	Day	12% 8% 35% 30% 12% 4	452
	21st to end	Day	17% 9% 28% 30% 12% 3	460
May	1st to 10th	Day	15% 10% 23% 28% 18% 5%	629
	11th to 20th	Day	12% 7% 21% 31% 22% 6%	675
	21st to end	Day	17% 6% 19% 28% 20% 9%	734
June	1st to 10th	Day	16% 7% 24% 33% 16% 4	680
	11th to 20th	Day	17% 11% 26% 27% 15% 4	680
	21st to end	Day	10% 6% 23% 30% 23% 8%	680
July	1st to 10th	Day	8% 3 19% 34% 29% 7%	671
	11th to 20th	Day	12% 5% 21% 32% 22% 8%	668
	21st to end	Day	5% 5% 18% 32% 29% 11%	739
August	1st to 10th	Day	10% 5% 21% 30% 24% 10%	573
	11th to 20th	Day	8% 5% 19% 34% 27% 7%	477
	21st to end	Day	9% 7% 22% 29% 26% 8%	539
September	1st to 10th	Day	12% 8% 27% 29% 20% 4	490
	11th to 20th	Day	18% 5% 24% 32% 17% 4	490
	21st to end	Day	13% 12% 28% 27% 16% 3	490
October	1st to 10th	Day	15% 7% 29% 27% 17% 5%	329
	11th to 20th	Day	9% 10% 31% 33% 15% 2	300
	21st to end	Day	11% 11% 36% 28% 12% 2	330
November	1st to 10th	Day	15% 8% 30% 32% 13% 2	300
	11th to 20th	Day	13% 9% 39% 26% 13% 1	269
	21st to end	Day	9% 7% 34% 29% 15% 6%	180
December	1st to 10th	Day	10% 7% 35% 29% 16% 3	180
	11th to 20th	Day	6% 12% 33% 33% 13% 2	180
	21st to end	Day	10% 9% 21% 33% 20% 7%	198
January	1st to 10th	Night	8% 7% 36% 34% 14% 1	950
	11th to 20th	Night	9% 10% 33% 34% 12% 1	950
	21st to end	Night	11% 10% 32% 32% 13% 2	960
February	1st to 10th	Night	11% 9% 25% 35% 16% 3	760
	11th to 20th	Night	10% 5% 36% 33% 14% 1	744
	21st to end	Night	7% 4 25% 39% 20% 5%	628
March	1st to 10th	Night	7% 5% 32% 38% 16% 3	760
	11th to 20th	Night	10% 6% 31% 38% 12% 3	760
	21st to end	Night	13% 6% 29% 34% 14% 4	836
April	1st to 10th	Night	11% 7% 32% 31% 16% 3	622
	11th to 20th	Night	14% 7% 34% 33% 11% 1	563
	21st to end	Night	15% 7% 25% 40% 12% 1	570
May	1st to 10th	Night	17% 7% 24% 35% 15% 2	553
	11th to 20th	Night	9% 6% 24% 38% 21% 2	374
	21st to end	Night	19% 5% 22% 29% 23% 2	411
June	1st to 10th	Night	17% 8% 26% 33% 14% 2	380
	11th to 20th	Night	18% 7% 26% 31% 17% 2	380
	21st to end	Night	12% 3 24% 35% 25% 2	380
July	1st to 10th	Night	11% 3 23% 42% 20% 1	370
	11th to 20th	Night	10% 3 25% 40% 20% 1	368
	21st to end	Night	4 4 22% 41% 27% 3	416
August	1st to 10th	Night	7% 4 23% 37% 25% 4	413
	11th to 20th	Night	9% 6% 18% 42% 23% 1	564
	21st to end	Night	8% 4 23% 38% 24% 1	627
September	1st to 10th	Night	11% 4 25% 39% 20% 2	570
	11th to 20th	Night	16% 3 22% 41% 17% 1	739
	21st to end	Night	9% 6% 30% 39% 15% 1	760
October	1st to 10th	Night	13% 5% 28% 37% 16% 2	760
	11th to 20th	Night	9% 5% 34% 35% 14% 2	760
	21st to end	Night	10% 9% 32% 37% 11% 1	864
November	1st to 10th	Night	15% 8% 31% 35% 9% 1	975
	11th to 20th	Night	9% 8% 37% 33% 10% 2	956
	21st to end	Night	7% 6% 36% 37% 12% 1	950
December	1st to 10th	Night	11% 7% 32% 32% 15% 3	950
	11th to 20th	Night	9% 8% 36% 33% 12% 2	950
	21st to end	Night	10% 4 34% 33% 15% 3	1045

Page generated at 2024-11-08 20:45:40. Version ac07

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