Gibsons
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gibsons clear sky chart from 2005-11-06 to 2025-02-25.

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	22% 8% 3 6% 4 4 4 3 5% 6% 36%	112157
	Night	27% 9% 3 6% 4 4 4 3 4 5% 31%	115186
Transparency	Day	49% 10% 14% 18% 8% 1	111903
	Night	55% 8% 13% 17% 7% 1	115086
Seeing	Day	23% 7% 20% 27% 20% 4	15738
	Night	31% 6% 17% 24% 18% 4	24062

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	39% 11% 4 8% 5% 4 4 3 4 5% 14%	3179
	11th to 20th	Day	21% 11% 2 6% 5% 5% 5% 3 5% 7% 30%	3159
	21st to end	Day	45% 8% 2 5% 4 3 3 2 3 4 21%	3951
February	1st to 10th	Day	31% 10% 3 7% 6% 6% 4 5% 5% 5% 17%	1800
	11th to 20th	Day	28% 11% 3 7% 4 4 4 4 5% 6% 24%	1755
	21st to end	Day	26% 10% 4 9% 5% 5% 5% 4 5% 6% 23%	1450
March	1st to 10th	Day	25% 12% 4 9% 5% 5% 5% 4 6% 7% 17%	3276
	11th to 20th	Day	23% 8% 3 7% 4 4 4 3 5% 6% 33%	3490
	21st to end	Day	26% 13% 4 7% 5% 4 4 3 4 5% 26%	3901
April	1st to 10th	Day	25% 11% 4 8% 5% 4 5% 4 6% 6% 23%	2280
	11th to 20th	Day	23% 8% 3 7% 5% 4 4 4 6% 6% 29%	2375
	21st to end	Day	22% 10% 3 7% 4 4 5% 3 5% 6% 31%	2508
May	1st to 10th	Day	15% 7% 2 6% 4 4 4 3 4 6% 45%	4420
	11th to 20th	Day	10% 6% 2 6% 4 4 4 4 8% 12% 40%	4377
	21st to end	Day	25% 8% 3 6% 4 4 5% 4 5% 7% 29%	4993
June	1st to 10th	Day	20% 8% 3 7% 5% 4 4 4 6% 7% 32%	2850
	11th to 20th	Day	17% 7% 3 7% 5% 5% 5% 5% 6% 7% 32%	2850
	21st to end	Day	15% 6% 2 6% 5% 5% 5% 4 5% 8% 41%	2850
July	1st to 10th	Day	6% 4 1 4 3 2 2 2 4 4 66%	4740
	11th to 20th	Day	5% 3 1 2 2 2 2 2 4 5% 71%	4740
	21st to end	Day	11% 5% 2 5% 4 3 3 3 5% 6% 55%	4952
August	1st to 10th	Day	5% 2 1 3 2 2 3 2 4 6% 69%	4323
	11th to 20th	Day	12% 7% 3 7% 4 3 3 4 5% 7% 45%	4026
	21st to end	Day	15% 6% 2 6% 4 4 3 4 5% 6% 46%	4459
September	1st to 10th	Day	11% 6% 3 5% 3 3 4 3 5% 7% 50%	2280
	11th to 20th	Day	18% 7% 3 6% 4 3 4 3 4 6% 42%	2252
	21st to end	Day	24% 6% 2 4 4 4 3 4 6% 8% 37%	2018
October	1st to 10th	Day	24% 8% 3 8% 5% 4 5% 3 5% 7% 29%	3180
	11th to 20th	Day	35% 6% 2 6% 4 4 3 3 4 6% 26%	3161
	21st to end	Day	31% 11% 3 8% 4 4 3 2 5% 7% 21%	3158
November	1st to 10th	Day	40% 10% 2 7% 3 4 4 3 3 5% 19%	1568
	11th to 20th	Day	37% 10% 2 5% 4 3 3 4 3 6% 22%	1600
	21st to end	Day	39% 11% 3 6% 3 4 3 3 4 4 20%	1600
December	1st to 10th	Day	24% 10% 3 9% 6% 4 4 3 4 6% 27%	2493
	11th to 20th	Day	43% 14% 4 7% 4 4 3 3 3 4 12%	2645
	21st to end	Day	43% 13% 4 9% 5% 3 3 2 3 3 10%	3498
January	1st to 10th	Night	38% 13% 4 9% 5% 4 4 2 3 4 16%	6766
	11th to 20th	Night	23% 8% 3 7% 4 4 4 3 5% 7% 31%	6739
	21st to end	Night	40% 9% 2 5% 3 3 3 2 3 5% 24%	7005
February	1st to 10th	Night	31% 12% 3 7% 4 5% 4 4 5% 5% 20%	2600
	11th to 20th	Night	27% 12% 3 6% 4 4 4 3 4 5% 28%	2532
	21st to end	Night	29% 12% 3 7% 4 4 4 3 4 5% 25%	2098
March	1st to 10th	Night	29% 14% 4 6% 4 4 4 3 4 5% 22%	3594
	11th to 20th	Night	22% 8% 3 7% 4 4 4 3 4 6% 36%	3489
	21st to end	Night	29% 15% 4 8% 5% 4 4 3 3 4 21%	3751
April	1st to 10th	Night	26% 11% 3 7% 5% 5% 6% 4 5% 6% 23%	1900
	11th to 20th	Night	20% 10% 3 8% 6% 4 4 4 5% 6% 30%	1753
	21st to end	Night	23% 9% 3 7% 6% 5% 4 3 5% 6% 29%	1672
May	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 4 5% 47%	2540
	11th to 20th	Night	12% 5% 2 4 3 4 3 3 6% 10% 47%	2516
	21st to end	Night	19% 11% 4 9% 6% 5% 4 3 4 6% 29%	2580
June	1st to 10th	Night	21% 8% 2 9% 5% 5% 4 3 4 5% 33%	1330
	11th to 20th	Night	16% 9% 4 7% 5% 5% 5% 4 6% 7% 33%	1330
	21st to end	Night	10% 6% 2 7% 6% 5% 6% 4 6% 8% 42%	1330
July	1st to 10th	Night	6% 3 1 4 3 3 3 3 4 5% 65%	2220
	11th to 20th	Night	3 3 1 3 2 2 2 2 3 5% 74%	2220
	21st to end	Night	8% 6% 2 5% 3 3 3 4 5% 6% 54%	2598
August	1st to 10th	Night	4 2 1 2 2 2 2 2 3 5% 74%	2607
	11th to 20th	Night	10% 5% 2 6% 4 4 4 4 5% 7% 48%	2812
	21st to end	Night	14% 5% 2 6% 4 5% 4 3 5% 6% 45%	3210
September	1st to 10th	Night	9% 4 2 4 3 4 4 3 5% 6% 57%	1900
	11th to 20th	Night	20% 6% 2 5% 3 3 4 3 5% 6% 44%	1926
	21st to end	Night	21% 7% 2 6% 4 4 3 3 4 6% 40%	2162
October	1st to 10th	Night	22% 8% 3 7% 4 4 5% 3 5% 7% 32%	3800
	11th to 20th	Night	31% 8% 3 6% 3 4 3 3 4 6% 29%	3777
	21st to end	Night	33% 9% 3 7% 4 3 3 2 3 5% 28%	4399
November	1st to 10th	Night	39% 10% 3 7% 5% 4 3 3 3 4 19%	2730
	11th to 20th	Night	35% 10% 3 6% 4 4 3 3 4 4 24%	2800
	21st to end	Night	37% 10% 3 7% 5% 4 3 2 4 5% 21%	2800
December	1st to 10th	Night	27% 11% 3 7% 4 4 4 4 4 7% 25%	4682
	11th to 20th	Night	43% 13% 3 8% 4 3 3 3 4 4 12%	5560
	21st to end	Night	43% 15% 4 7% 4 3 3 2 3 3 13%	7458

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% 9% 8% 9% 3 1	3179
	11th to 20th	Day	50% 8% 17% 15% 8% 1	3180
	21st to end	Day	66% 7% 8% 15% 4	3951
February	1st to 10th	Day	67% 10% 8% 9% 4 3	1800
	11th to 20th	Day	60% 10% 9% 14% 6% 1	1764
	21st to end	Day	61% 12% 11% 9% 5% 2	1450
March	1st to 10th	Day	62% 12% 14% 8% 4	3276
	11th to 20th	Day	53% 7% 13% 23% 4 1	3490
	21st to end	Day	60% 11% 16% 10% 3	3901
April	1st to 10th	Day	61% 12% 13% 10% 4	2280
	11th to 20th	Day	54% 10% 12% 13% 9% 2	2375
	21st to end	Day	56% 11% 11% 14% 7% 1	2508
May	1st to 10th	Day	41% 10% 15% 21% 12% 1	4420
	11th to 20th	Day	37% 15% 22% 20% 5%	4380
	21st to end	Day	54% 13% 16% 14% 3	4994
June	1st to 10th	Day	51% 11% 16% 14% 5% 2	2850
	11th to 20th	Day	50% 15% 17% 14% 5%	2850
	21st to end	Day	42% 12% 17% 18% 9% 2	2850
July	1st to 10th	Day	23% 8% 11% 26% 23% 9%	4666
	11th to 20th	Day	17% 7% 16% 39% 21% 1	4659
	21st to end	Day	29% 11% 21% 25% 13% 2	4795
August	1st to 10th	Day	18% 8% 13% 47% 13% 1	4306
	11th to 20th	Day	36% 12% 25% 17% 8% 1	4065
	21st to end	Day	40% 10% 19% 21% 10% 1	4458
September	1st to 10th	Day	34% 11% 14% 25% 12% 3	2280
	11th to 20th	Day	44% 10% 13% 17% 14% 2	2252
	21st to end	Day	48% 10% 16% 16% 9% 1	2018
October	1st to 10th	Day	55% 9% 15% 16% 5%	3180
	11th to 20th	Day	59% 9% 11% 15% 6%	3161
	21st to end	Day	63% 10% 11% 11% 4 1	3158
November	1st to 10th	Day	68% 8% 10% 8% 5% 1	1568
	11th to 20th	Day	66% 8% 10% 10% 5% 2	1600
	21st to end	Day	68% 8% 7% 11% 7% 1	1600
December	1st to 10th	Day	56% 9% 12% 17% 5% 1	2493
	11th to 20th	Day	77% 6% 9% 6% 2 1	2648
	21st to end	Day	79% 8% 6% 5% 2 1	3498
January	1st to 10th	Night	72% 6% 7% 12% 3	6766
	11th to 20th	Night	49% 8% 19% 17% 6% 1	6780
	21st to end	Night	63% 6% 10% 18% 3	7005
February	1st to 10th	Night	66% 7% 9% 10% 6% 3	2600
	11th to 20th	Night	60% 8% 10% 13% 7% 1	2534
	21st to end	Night	62% 7% 10% 13% 6% 2	2098
March	1st to 10th	Night	62% 9% 13% 11% 6%	3594
	11th to 20th	Night	49% 8% 14% 24% 4	3490
	21st to end	Night	66% 8% 11% 12% 2	3751
April	1st to 10th	Night	60% 9% 13% 15% 3	1900
	11th to 20th	Night	54% 8% 11% 15% 9% 2	1753
	21st to end	Night	56% 9% 12% 14% 9%	1672
May	1st to 10th	Night	39% 7% 14% 28% 11% 1	2540
	11th to 20th	Night	32% 9% 25% 27% 7%	2516
	21st to end	Night	58% 7% 16% 15% 3	2580
June	1st to 10th	Night	52% 7% 16% 17% 5% 3	1330
	11th to 20th	Night	50% 11% 17% 17% 5%	1330
	21st to end	Night	40% 10% 19% 19% 9% 3	1330
July	1st to 10th	Night	21% 6% 11% 30% 26% 6%	2185
	11th to 20th	Night	15% 5% 13% 43% 23% 1	2178
	21st to end	Night	28% 8% 16% 29% 16% 3	2516
August	1st to 10th	Night	14% 6% 15% 42% 22% 2	2599
	11th to 20th	Night	33% 11% 28% 16% 9% 3	2839
	21st to end	Night	40% 8% 18% 24% 11%	3210
September	1st to 10th	Night	28% 9% 17% 28% 13% 5%	1900
	11th to 20th	Night	42% 9% 12% 17% 16% 4	1926
	21st to end	Night	48% 7% 15% 21% 9% 2	2162
October	1st to 10th	Night	51% 9% 18% 14% 7%	3800
	11th to 20th	Night	58% 6% 12% 18% 6%	3777
	21st to end	Night	60% 8% 11% 16% 5%	4399
November	1st to 10th	Night	69% 6% 10% 9% 4 1	2730
	11th to 20th	Night	66% 7% 10% 10% 6% 2	2800
	21st to end	Night	66% 7% 9% 10% 7% 1	2800
December	1st to 10th	Night	58% 8% 14% 15% 4 1	4682
	11th to 20th	Night	76% 7% 7% 6% 3	5556
	21st to end	Night	76% 7% 8% 7% 2	7458

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	42% 11% 19% 17% 8% 5%	200
	11th to 20th	Day	39% 13% 16% 21% 13% 1	200
	21st to end	Day	42% 9% 20% 17% 10% 2	262
February	1st to 10th	Day	35% 10% 26% 19% 10% 1	400
	11th to 20th	Day	33% 7% 26% 24% 9% 2	395
	21st to end	Day	30% 11% 26% 22% 11% 1	320
March	1st to 10th	Day	30% 10% 25% 23% 9% 2	458
	11th to 20th	Day	30% 10% 19% 25% 14% 2	460
	21st to end	Day	32% 9% 25% 21% 11% 1	506
April	1st to 10th	Day	29% 10% 24% 22% 13% 1	460
	11th to 20th	Day	27% 8% 27% 22% 14% 2	452
	21st to end	Day	24% 8% 27% 23% 16% 1	460
May	1st to 10th	Day	16% 7% 21% 37% 19% 2	463
	11th to 20th	Day	17% 5% 17% 31% 27% 3	488
	21st to end	Day	16% 6% 21% 31% 21% 4	631
June	1st to 10th	Day	20% 5% 22% 30% 21% 2	680
	11th to 20th	Day	16% 5% 25% 31% 19% 3	680
	21st to end	Day	14% 3 18% 34% 27% 4	680
July	1st to 10th	Day	13% 3 15% 34% 31% 5%	671
	11th to 20th	Day	7% 2 16% 37% 32% 5%	668
	21st to end	Day	7% 4 12% 33% 37% 7%	628
August	1st to 10th	Day	9% 2 13% 26% 38% 11%	487
	11th to 20th	Day	8% 4 11% 35% 35% 7%	477
	21st to end	Day	12% 5% 17% 38% 24% 3	539
September	1st to 10th	Day	16% 4 19% 35% 21% 5%	490
	11th to 20th	Day	22% 7% 18% 27% 21% 5%	490
	21st to end	Day	24% 6% 23% 27% 16% 4	490
October	1st to 10th	Day	28% 5% 18% 26% 18% 4	490
	11th to 20th	Day	38% 6% 14% 21% 17% 4	490
	21st to end	Day	36% 12% 18% 21% 9% 3	403
November	1st to 10th	Day	38% 13% 23% 15% 12%	200
	11th to 20th	Day	41% 8% 13% 21% 14% 5%	200
	21st to end	Day	43% 13% 18% 11% 10% 7%	200
December	1st to 10th	Day	42% 4 19% 15% 16% 5%	200
	11th to 20th	Day	41% 12% 20% 20% 7% 1	200
	21st to end	Day	44% 9% 27% 16% 4	220
January	1st to 10th	Night	47% 9% 19% 14% 10% 1	900
	11th to 20th	Night	40% 7% 16% 23% 13%	900
	21st to end	Night	39% 6% 19% 24% 11% 1	913
February	1st to 10th	Night	36% 7% 22% 24% 11%	800
	11th to 20th	Night	33% 7% 23% 26% 10% 1	784
	21st to end	Night	36% 10% 21% 20% 10% 3	646
March	1st to 10th	Night	34% 7% 21% 22% 14% 2	760
	11th to 20th	Night	35% 9% 17% 24% 14% 1	760
	21st to end	Night	37% 6% 18% 23% 14% 2	836
April	1st to 10th	Night	31% 8% 16% 27% 14% 4	760
	11th to 20th	Night	25% 7% 26% 26% 14% 2	625
	21st to end	Night	27% 7% 21% 29% 16% 1	532
May	1st to 10th	Night	17% 3 19% 33% 23% 5%	380
	11th to 20th	Night	18% 4 11% 29% 31% 7%	374
	21st to end	Night	18% 4 15% 31% 27% 5%	411
June	1st to 10th	Night	24% 3 14% 31% 24% 4	380
	11th to 20th	Night	18% 5% 13% 33% 23% 7%	380
	21st to end	Night	12% 3 11% 33% 36% 5%	380
July	1st to 10th	Night	12% 1 9% 26% 42% 9%	370
	11th to 20th	Night	9% 2 7% 30% 42% 11%	368
	21st to end	Night	6% 1 7% 25% 50% 11%	416
August	1st to 10th	Night	8% 2 5% 22% 43% 20%	417
	11th to 20th	Night	7% 1 5% 26% 46% 13%	564
	21st to end	Night	12% 3 11% 29% 38% 6%	665
September	1st to 10th	Night	9% 3 12% 34% 32% 10%	760
	11th to 20th	Night	21% 5% 14% 20% 29% 12%	760
	21st to end	Night	25% 6% 15% 26% 24% 4	760
October	1st to 10th	Night	23% 4 17% 30% 23% 3	760
	11th to 20th	Night	35% 4 15% 27% 17% 3	760
	21st to end	Night	39% 7% 19% 24% 9% 2	836
November	1st to 10th	Night	43% 9% 19% 24% 6%	780
	11th to 20th	Night	41% 7% 21% 20% 10% 1	800
	21st to end	Night	43% 5% 21% 20% 10% 2	800
December	1st to 10th	Night	36% 7% 18% 27% 11% 1	835
	11th to 20th	Night	49% 7% 22% 16% 5%	900
	21st to end	Night	47% 9% 24% 15% 4	990

Page generated at 2025-02-22 03:51:35. Version ac07

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