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 2024-01-13.

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	9% 8% 4 7% 7% 4 5% 5% 6% 8% 36%	74663
	Night	7% 8% 4 8% 7% 4 6% 6% 6% 9% 35%	75091
Transparency	Day	44% 8% 17% 23% 9% 1	74344
	Night	44% 8% 16% 22% 10% 1	74928
Seeing	Day	12% 7% 26% 31% 19% 5%	14350
	Night	11% 6% 30% 36% 15% 2	23631

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% 10% 7% 7% 6% 7% 6% 9% 26%	1329
	11th to 20th	Day	5% 12% 6% 9% 9% 4 6% 6% 5% 10% 27%	1277
	21st to end	Day	4 11% 6% 12% 9% 5% 6% 7% 7% 7% 26%	1484
February	1st to 10th	Day	6% 13% 5% 10% 8% 5% 6% 5% 7% 9% 25%	1498
	11th to 20th	Day	6% 12% 6% 10% 8% 4 7% 7% 7% 8% 25%	1575
	21st to end	Day	6% 10% 5% 11% 9% 5% 6% 8% 7% 11% 23%	1336
March	1st to 10th	Day	7% 11% 5% 11% 12% 7% 7% 5% 5% 6% 26%	1843
	11th to 20th	Day	7% 10% 5% 8% 9% 4 6% 4 5% 9% 33%	1979
	21st to end	Day	8% 11% 5% 10% 9% 4 5% 5% 7% 6% 29%	2178
April	1st to 10th	Day	9% 10% 5% 8% 8% 4 5% 6% 6% 9% 31%	2231
	11th to 20th	Day	11% 12% 5% 8% 6% 3 5% 5% 6% 8% 31%	2310
	21st to end	Day	13% 9% 4 7% 6% 4 5% 5% 5% 9% 31%	2340
May	1st to 10th	Day	12% 9% 4 8% 8% 4 7% 5% 7% 7% 28%	2510
	11th to 20th	Day	8% 6% 4 6% 6% 4 6% 6% 6% 9% 39%	2654
	21st to end	Day	18% 7% 4 7% 6% 4 5% 5% 6% 8% 31%	2917
June	1st to 10th	Day	16% 7% 3 6% 7% 4 5% 6% 7% 10% 31%	2700
	11th to 20th	Day	19% 8% 4 8% 6% 4 5% 6% 5% 8% 27%	2700
	21st to end	Day	9% 5% 2 5% 7% 4 7% 7% 7% 9% 40%	2700
July	1st to 10th	Day	8% 4 3 6% 6% 3 5% 6% 7% 9% 42%	2700
	11th to 20th	Day	11% 4 2 5% 5% 3 5% 5% 7% 10% 43%	2700
	21st to end	Day	5% 3 2 4 5% 3 6% 5% 5% 10% 52%	2938
August	1st to 10th	Day	9% 5% 2 5% 4 4 5% 5% 7% 10% 44%	2555
	11th to 20th	Day	9% 5% 2 4 4 3 5% 5% 6% 9% 48%	2299
	21st to end	Day	8% 5% 2 5% 5% 3 5% 6% 6% 9% 46%	2574
September	1st to 10th	Day	11% 7% 2 5% 4 3 4 5% 5% 8% 45%	2263
	11th to 20th	Day	16% 6% 2 4 5% 3 4 4 6% 7% 43%	1998
	21st to end	Day	8% 7% 3 5% 5% 3 4 4 5% 9% 48%	1980
October	1st to 10th	Day	10% 10% 4 6% 6% 4 4 4 5% 6% 42%	1828
	11th to 20th	Day	8% 9% 4 7% 5% 4 5% 5% 5% 8% 41%	1746
	21st to end	Day	6% 11% 4 7% 7% 4 5% 6% 6% 9% 34%	1737
November	1st to 10th	Day	8% 13% 7% 9% 8% 4 6% 5% 5% 7% 27%	1488
	11th to 20th	Day	5% 11% 6% 10% 9% 4 5% 5% 5% 7% 33%	1512
	21st to end	Day	6% 9% 4 12% 7% 4 6% 6% 7% 8% 32%	1330
December	1st to 10th	Day	7% 11% 4 13% 8% 6% 7% 6% 6% 9% 24%	1330
	11th to 20th	Day	4 9% 6% 13% 9% 6% 7% 6% 7% 6% 27%	1682
	21st to end	Day	5% 8% 3 8% 6% 3 4 4 6% 8% 44%	2442
January	1st to 10th	Night	5% 9% 5% 10% 10% 6% 7% 8% 8% 9% 25%	2836
	11th to 20th	Night	5% 10% 5% 9% 9% 5% 6% 6% 6% 10% 29%	2745
	21st to end	Night	5% 11% 5% 11% 8% 5% 7% 6% 7% 9% 25%	2889
February	1st to 10th	Night	6% 8% 5% 9% 9% 4 6% 6% 8% 9% 30%	2462
	11th to 20th	Night	5% 12% 5% 10% 9% 5% 7% 7% 8% 8% 24%	2272
	21st to end	Night	5% 7% 5% 9% 8% 6% 5% 7% 8% 10% 30%	1916
March	1st to 10th	Night	4 10% 5% 10% 10% 5% 7% 6% 6% 9% 28%	2117
	11th to 20th	Night	6% 9% 5% 8% 8% 5% 7% 6% 7% 10% 32%	1980
	21st to end	Night	8% 11% 5% 9% 8% 4 6% 6% 8% 8% 27%	2178
April	1st to 10th	Night	7% 9% 5% 8% 6% 5% 6% 5% 6% 8% 34%	1726
	11th to 20th	Night	9% 10% 4 9% 9% 3 4 6% 7% 8% 31%	1601
	21st to end	Night	10% 9% 4 8% 6% 4 5% 6% 6% 8% 33%	1620
May	1st to 10th	Night	12% 10% 4 7% 7% 4 5% 6% 6% 7% 32%	1447
	11th to 20th	Night	10% 6% 3 7% 6% 4 7% 7% 6% 8% 38%	1239
	21st to end	Night	17% 6% 3 5% 6% 5% 6% 6% 5% 8% 33%	1358
June	1st to 10th	Night	15% 7% 3 7% 6% 4 6% 5% 7% 8% 31%	1260
	11th to 20th	Night	15% 8% 2 6% 7% 4 6% 6% 6% 8% 31%	1260
	21st to end	Night	10% 4 2 5% 6% 3 6% 5% 6% 9% 44%	1260
July	1st to 10th	Night	7% 5% 2 5% 6% 3 5% 6% 8% 11% 42%	1260
	11th to 20th	Night	8% 5% 2 4 5% 2 6% 6% 7% 12% 43%	1260
	21st to end	Night	4 3 1 5% 4 3 4 6% 5% 9% 55%	1379
August	1st to 10th	Night	7% 6% 2 5% 5% 3 6% 7% 7% 10% 42%	1381
	11th to 20th	Night	9% 5% 3 6% 5% 4 5% 4 6% 9% 45%	1602
	21st to end	Night	8% 4 2 5% 5% 3 5% 5% 7% 9% 47%	1782
September	1st to 10th	Night	8% 5% 2 6% 6% 4 5% 4 6% 7% 47%	1697
	11th to 20th	Night	14% 7% 1 4 4 3 4 4 5% 8% 46%	1960
	21st to end	Night	7% 6% 2 6% 4 3 5% 5% 6% 8% 48%	1980
October	1st to 10th	Night	10% 9% 3 6% 5% 4 4 5% 6% 9% 40%	2132
	11th to 20th	Night	8% 6% 3 8% 7% 3 5% 6% 6% 8% 40%	2214
	21st to end	Night	6% 10% 4 7% 7% 4 6% 7% 7% 10% 32%	2600
November	1st to 10th	Night	10% 12% 6% 7% 7% 4 5% 5% 6% 7% 32%	2590
	11th to 20th	Night	5% 9% 6% 9% 8% 4 7% 6% 6% 8% 32%	2664
	21st to end	Night	5% 9% 5% 10% 8% 4 6% 5% 7% 9% 31%	2850
December	1st to 10th	Night	8% 10% 6% 11% 9% 5% 7% 5% 5% 9% 27%	2850
	11th to 20th	Night	5% 9% 5% 11% 10% 4 6% 6% 7% 9% 29%	3510
	21st to end	Night	4 7% 4 7% 7% 4 6% 5% 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	53% 8% 12% 20% 7% 1	1329
	11th to 20th	Day	52% 8% 15% 16% 8% 1	1277
	21st to end	Day	54% 8% 14% 15% 9% 1	1484
February	1st to 10th	Day	52% 6% 15% 18% 8%	1498
	11th to 20th	Day	54% 8% 14% 15% 9%	1584
	21st to end	Day	53% 6% 15% 17% 9%	1336
March	1st to 10th	Day	57% 7% 16% 14% 6%	1843
	11th to 20th	Day	48% 7% 13% 22% 9% 1	1980
	21st to end	Day	53% 8% 17% 17% 5%	2178
April	1st to 10th	Day	47% 7% 18% 19% 9% 1	2231
	11th to 20th	Day	50% 6% 13% 21% 9%	2310
	21st to end	Day	47% 8% 15% 21% 7% 2	2340
May	1st to 10th	Day	50% 8% 15% 19% 8%	2510
	11th to 20th	Day	39% 7% 15% 26% 12% 1	2658
	21st to end	Day	49% 7% 15% 20% 9%	2918
June	1st to 10th	Day	45% 8% 17% 22% 8%	2700
	11th to 20th	Day	54% 7% 16% 17% 5% 1	2700
	21st to end	Day	36% 10% 23% 22% 7% 1	2700
July	1st to 10th	Day	33% 10% 22% 27% 7% 1	2626
	11th to 20th	Day	35% 9% 21% 26% 8%	2619
	21st to end	Day	26% 9% 23% 31% 11% 1	2775
August	1st to 10th	Day	32% 10% 23% 26% 8% 1	2537
	11th to 20th	Day	30% 9% 23% 27% 10% 1	2299
	21st to end	Day	32% 7% 19% 31% 11% 1	2574
September	1st to 10th	Day	35% 7% 17% 25% 11% 4	2263
	11th to 20th	Day	40% 5% 16% 29% 8% 1	1998
	21st to end	Day	34% 7% 16% 30% 11% 2	1980
October	1st to 10th	Day	42% 6% 17% 24% 11%	1828
	11th to 20th	Day	40% 7% 17% 25% 10% 1	1746
	21st to end	Day	45% 7% 14% 23% 10% 1	1737
November	1st to 10th	Day	55% 6% 13% 18% 6% 1	1488
	11th to 20th	Day	50% 8% 14% 22% 6%	1512
	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	51% 9% 16% 17% 6% 2	2836
	11th to 20th	Night	48% 7% 16% 19% 7% 2	2745
	21st to end	Night	53% 8% 14% 17% 8% 1	2889
February	1st to 10th	Night	47% 7% 15% 20% 11%	2462
	11th to 20th	Night	54% 7% 14% 17% 8%	2273
	21st to end	Night	44% 8% 14% 22% 10% 1	1916
March	1st to 10th	Night	50% 8% 15% 21% 7%	2117
	11th to 20th	Night	45% 8% 12% 24% 9% 1	1980
	21st to end	Night	49% 9% 15% 19% 7% 1	2178
April	1st to 10th	Night	44% 7% 15% 20% 12% 1	1726
	11th to 20th	Night	48% 7% 12% 23% 10% 1	1601
	21st to end	Night	44% 8% 14% 23% 10% 2	1620
May	1st to 10th	Night	47% 7% 11% 23% 11% 1	1447
	11th to 20th	Night	38% 10% 13% 25% 13% 2	1239
	21st to end	Night	46% 8% 14% 21% 10% 1	1358
June	1st to 10th	Night	48% 8% 14% 21% 8% 1	1260
	11th to 20th	Night	47% 9% 17% 18% 9% 1	1260
	21st to end	Night	34% 10% 22% 26% 8% 1	1260
July	1st to 10th	Night	32% 10% 23% 26% 8% 1	1225
	11th to 20th	Night	31% 10% 26% 23% 9% 1	1218
	21st to end	Night	23% 8% 23% 32% 12% 1	1302
August	1st to 10th	Night	33% 9% 23% 27% 8% 1	1374
	11th to 20th	Night	35% 7% 19% 29% 9% 1	1602
	21st to end	Night	31% 7% 16% 30% 15% 2	1782
September	1st to 10th	Night	33% 9% 18% 20% 14% 6%	1697
	11th to 20th	Night	36% 7% 14% 29% 12% 3	1960
	21st to end	Night	33% 7% 16% 27% 16% 2	1980
October	1st to 10th	Night	40% 6% 15% 25% 11% 2	2132
	11th to 20th	Night	41% 6% 17% 25% 11% 1	2214
	21st to end	Night	43% 9% 16% 23% 7% 1	2600
November	1st to 10th	Night	50% 7% 13% 19% 9% 1	2590
	11th to 20th	Night	47% 8% 16% 19% 9%	2664
	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% 30% 19% 6%	180
	11th to 20th	Day	7% 8% 32% 33% 16% 5%	165
	21st to end	Day	9% 10% 37% 26% 13% 5%	176
February	1st to 10th	Day	16% 8% 31% 34% 8% 3	186
	11th to 20th	Day	14% 7% 32% 37% 10% 1	240
	21st to end	Day	6% 2 35% 26% 26% 4	202
March	1st to 10th	Day	9% 8% 34% 31% 15% 3	420
	11th to 20th	Day	9% 7% 36% 30% 13% 5%	420
	21st to end	Day	11% 9% 29% 33% 15% 3	462
April	1st to 10th	Day	10% 14% 30% 31% 11% 4	420
	11th to 20th	Day	12% 8% 33% 30% 12% 4	412
	21st to end	Day	18% 8% 29% 30% 12% 3	420
May	1st to 10th	Day	14% 11% 23% 29% 18% 5%	580
	11th to 20th	Day	11% 7% 21% 31% 23% 6%	625
	21st to end	Day	18% 6% 19% 29% 19% 9%	679
June	1st to 10th	Day	16% 6% 23% 34% 17% 4	630
	11th to 20th	Day	18% 11% 26% 26% 15% 4	630
	21st to end	Day	10% 5% 22% 30% 24% 9%	630
July	1st to 10th	Day	9% 4 19% 34% 28% 7%	621
	11th to 20th	Day	13% 6% 21% 33% 21% 7%	618
	21st to end	Day	5% 5% 18% 33% 28% 11%	684
August	1st to 10th	Day	11% 5% 21% 30% 23% 10%	529
	11th to 20th	Day	9% 5% 20% 33% 27% 6%	437
	21st to end	Day	8% 7% 21% 30% 26% 8%	495
September	1st to 10th	Day	13% 8% 28% 30% 18% 3	450
	11th to 20th	Day	18% 5% 24% 32% 17% 4	450
	21st to end	Day	14% 12% 27% 28% 17% 3	450
October	1st to 10th	Day	16% 7% 28% 27% 18% 4	298
	11th to 20th	Day	10% 10% 30% 33% 14% 2	270
	21st to end	Day	11% 11% 37% 28% 11% 1	297
November	1st to 10th	Day	16% 8% 30% 30% 13% 3	270
	11th to 20th	Day	13% 9% 38% 26% 13% 1	266
	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	10% 10% 33% 34% 13% 1	915
	21st to end	Night	11% 10% 33% 32% 12% 2	909
February	1st to 10th	Night	11% 9% 25% 35% 16% 3	720
	11th to 20th	Night	11% 5% 37% 33% 13% 1	704
	21st to end	Night	7% 4 23% 40% 20% 6%	592
March	1st to 10th	Night	8% 4 32% 38% 16% 3	720
	11th to 20th	Night	10% 6% 30% 39% 12% 3	720
	21st to end	Night	14% 6% 28% 34% 14% 4	792
April	1st to 10th	Night	10% 7% 31% 32% 16% 4	590
	11th to 20th	Night	14% 7% 33% 33% 11% 1	533
	21st to end	Night	15% 7% 25% 40% 12% 1	540
May	1st to 10th	Night	16% 7% 24% 35% 15% 2	524
	11th to 20th	Night	10% 6% 24% 38% 21% 2	354
	21st to end	Night	19% 5% 22% 29% 23% 2	389
June	1st to 10th	Night	17% 8% 24% 34% 14% 2	360
	11th to 20th	Night	18% 7% 26% 31% 17% 2	360
	21st to end	Night	11% 3 23% 35% 26% 2	360
July	1st to 10th	Night	12% 3 23% 40% 21% 1	350
	11th to 20th	Night	11% 3 26% 40% 19% 1	348
	21st to end	Night	5% 4 21% 41% 27% 3	394
August	1st to 10th	Night	6% 4 23% 37% 25% 4	391
	11th to 20th	Night	10% 7% 19% 41% 22% 1	534
	21st to end	Night	8% 4 24% 38% 25% 2	594
September	1st to 10th	Night	11% 4 26% 39% 19% 2	540
	11th to 20th	Night	16% 3 21% 42% 17% 1	700
	21st to end	Night	9% 5% 30% 39% 16% 1	720
October	1st to 10th	Night	13% 5% 27% 37% 16% 2	720
	11th to 20th	Night	10% 5% 34% 35% 14% 3	720
	21st to end	Night	11% 9% 33% 37% 11% 1	818
November	1st to 10th	Night	15% 8% 32% 34% 10% 1	925
	11th to 20th	Night	9% 8% 38% 33% 10% 2	950
	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

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