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 2026-07-01.

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	21% 8% 3 6% 4 4 4 3 5% 6% 36%	141798
	Night	26% 9% 3 7% 4 4 4 3 4 6% 32%	139268
Transparency	Day	48% 10% 16% 18% 8% 1	141502
	Night	54% 7% 14% 17% 7% 1	139146
Seeing	Day	23% 7% 20% 27% 20% 4	17574
	Night	30% 6% 17% 24% 18% 4	25691

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	41% 12% 4 8% 5% 4 3 3 4 4 13%	4125
	11th to 20th	Day	22% 10% 2 5% 4 4 4 3 5% 6% 35%	4119
	21st to end	Day	43% 8% 2 5% 4 4 3 2 3 4 22%	5119
February	1st to 10th	Day	31% 10% 3 7% 6% 6% 4 5% 5% 5% 17%	1890
	11th to 20th	Day	27% 11% 3 7% 4 4 4 4 5% 6% 24%	1845
	21st to end	Day	25% 10% 4 9% 5% 6% 5% 4 5% 5% 23%	1557
March	1st to 10th	Day	26% 12% 4 10% 5% 5% 4 3 5% 6% 18%	4825
	11th to 20th	Day	26% 11% 3 8% 5% 4 4 3 5% 6% 26%	5110
	21st to end	Day	29% 13% 4 8% 5% 5% 4 3 4 5% 19%	5711
April	1st to 10th	Day	24% 11% 3 7% 5% 4 4 4 6% 6% 24%	2520
	11th to 20th	Day	22% 7% 3 7% 5% 4 5% 4 6% 7% 30%	2629
	21st to end	Day	21% 10% 3 7% 4 4 4 3 5% 6% 34%	2772
May	1st to 10th	Day	10% 6% 2 6% 4 4 5% 4 5% 6% 47%	8195
	11th to 20th	Day	14% 7% 3 7% 4 4 4 4 7% 10% 34%	8160
	21st to end	Day	17% 6% 2 6% 4 4 5% 4 6% 9% 36%	9327
June	1st to 10th	Day	19% 8% 3 7% 5% 4 4 4 6% 8% 34%	3150
	11th to 20th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 7% 34%	3150
	21st to end	Day	15% 6% 2 6% 5% 5% 5% 4 5% 8% 40%	3150
July	1st to 10th	Day	8% 4 2 5% 3 3 3 2 4 5% 62%	6781
	11th to 20th	Day	4 3 1 2 2 2 2 2 4 5% 72%	6780
	21st to end	Day	8% 4 2 4 3 2 3 2 4 6% 61%	7106
August	1st to 10th	Day	5% 2 1 3 2 2 3 2 4 7% 68%	4461
	11th to 20th	Day	12% 7% 3 7% 4 3 3 4 5% 7% 45%	4156
	21st to end	Day	14% 6% 2 6% 4 3 3 4 4 7% 46%	4600
September	1st to 10th	Day	11% 6% 2 6% 3 3 4 3 5% 7% 51%	2400
	11th to 20th	Day	18% 7% 3 6% 4 3 4 3 4 6% 43%	2370
	21st to end	Day	24% 6% 3 4 4 3 3 4 6% 7% 36%	2124
October	1st to 10th	Day	24% 8% 3 8% 5% 4 5% 3 5% 7% 29%	3280
	11th to 20th	Day	35% 6% 2 6% 4 4 3 3 4 6% 27%	3261
	21st to end	Day	32% 11% 3 8% 5% 4 3 2 5% 6% 20%	3258
November	1st to 10th	Day	39% 11% 2 8% 3 4 4 3 3 5% 19%	1648
	11th to 20th	Day	37% 10% 2 5% 4 3 3 4 3 6% 22%	1680
	21st to end	Day	40% 11% 3 6% 3 4 3 3 4 4 19%	1680
December	1st to 10th	Day	25% 10% 3 8% 6% 4 4 3 4 5% 26%	2569
	11th to 20th	Day	44% 13% 4 7% 4 4 3 3 3 3 12%	2715
	21st to end	Day	43% 14% 4 9% 5% 3 3 2 3 3 10%	3575
January	1st to 10th	Night	38% 12% 4 9% 4 4 4 2 4 4 15%	8770
	11th to 20th	Night	25% 7% 2 6% 4 3 3 3 5% 6% 35%	8779
	21st to end	Night	38% 8% 2 6% 4 3 3 3 3 5% 26%	9063
February	1st to 10th	Night	31% 13% 3 7% 4 5% 4 3 5% 5% 20%	2730
	11th to 20th	Night	27% 12% 3 6% 4 4 4 3 4 5% 28%	2662
	21st to end	Night	29% 12% 3 7% 4 4 4 3 4 5% 24%	2249
March	1st to 10th	Night	28% 12% 3 6% 4 4 4 3 4 6% 24%	5284
	11th to 20th	Night	26% 10% 3 7% 4 4 4 3 4 6% 28%	5109
	21st to end	Night	35% 13% 4 7% 4 3 4 3 4 4 18%	5505
April	1st to 10th	Night	24% 11% 3 7% 5% 5% 6% 4 5% 6% 24%	2100
	11th to 20th	Night	19% 10% 3 8% 6% 4 4 4 5% 6% 31%	1939
	21st to end	Night	22% 8% 3 7% 5% 5% 4 3 5% 6% 33%	1848
May	1st to 10th	Night	12% 6% 2 6% 3 4 3 3 4 5% 52%	4724
	11th to 20th	Night	12% 6% 3 8% 5% 5% 5% 4 6% 9% 37%	4700
	21st to end	Night	15% 8% 3 8% 6% 5% 5% 3 6% 8% 34%	4828
June	1st to 10th	Night	20% 8% 2 9% 5% 5% 5% 4 4 5% 34%	1470
	11th to 20th	Night	15% 8% 4 7% 5% 4 5% 4 6% 7% 35%	1470
	21st to end	Night	10% 7% 2 7% 6% 4 5% 3 6% 8% 41%	1470
July	1st to 10th	Night	8% 3 1 4 3 3 3 3 4 6% 61%	3180
	11th to 20th	Night	2 2 1 2 2 2 2 2 3 5% 77%	3180
	21st to end	Night	6% 5% 1 5% 3 3 3 3 4 7% 61%	3735
August	1st to 10th	Night	4 2 1 2 2 2 2 2 3 5% 74%	2689
	11th to 20th	Night	10% 5% 2 6% 4 5% 4 4 5% 7% 48%	2902
	21st to end	Night	14% 5% 2 6% 4 5% 4 3 5% 6% 46%	3311
September	1st to 10th	Night	9% 4 2 4 3 4 4 3 5% 6% 57%	2000
	11th to 20th	Night	19% 5% 2 5% 3 3 4 3 5% 6% 45%	2028
	21st to end	Night	22% 7% 2 6% 3 4 3 3 4 5% 40%	2276
October	1st to 10th	Night	22% 8% 3 7% 4 4 4 3 5% 7% 32%	3920
	11th to 20th	Night	31% 8% 3 6% 3 4 3 3 4 6% 29%	3897
	21st to end	Night	33% 9% 3 7% 4 3 3 3 4 5% 27%	4541
November	1st to 10th	Night	38% 10% 3 8% 5% 4 3 3 3 5% 18%	2870
	11th to 20th	Night	35% 9% 3 6% 4 4 3 3 4 4 24%	2940
	21st to end	Night	37% 10% 3 7% 5% 4 3 2 4 5% 21%	2940
December	1st to 10th	Night	28% 11% 3 7% 4 4 4 3 4 7% 25%	4826
	11th to 20th	Night	44% 13% 3 7% 4 3 3 3 4 4 12%	5710
	21st to end	Night	42% 14% 4 7% 4 3 3 3 3 3 13%	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	73% 9% 7% 8% 2	4125
	11th to 20th	Day	47% 7% 14% 21% 10% 1	4140
	21st to end	Day	66% 6% 7% 16% 5%	5120
February	1st to 10th	Day	67% 10% 8% 9% 4 3	1890
	11th to 20th	Day	60% 9% 10% 14% 6% 1	1854
	21st to end	Day	62% 12% 11% 9% 5% 2	1557
March	1st to 10th	Day	64% 10% 11% 10% 4	4825
	11th to 20th	Day	60% 7% 11% 19% 3 1	5110
	21st to end	Day	66% 10% 13% 8% 2	5711
April	1st to 10th	Day	59% 12% 14% 11% 4	2520
	11th to 20th	Day	53% 10% 13% 14% 9% 1	2629
	21st to end	Day	54% 10% 12% 16% 7% 1	2772
May	1st to 10th	Day	37% 8% 18% 24% 12% 1	8195
	11th to 20th	Day	42% 13% 23% 18% 4	8163
	21st to end	Day	44% 12% 21% 18% 5%	9328
June	1st to 10th	Day	49% 11% 17% 15% 6% 2	3150
	11th to 20th	Day	48% 14% 17% 16% 5%	3150
	21st to end	Day	43% 12% 18% 18% 8% 1	3150
July	1st to 10th	Day	25% 10% 18% 23% 17% 6%	6707
	11th to 20th	Day	15% 8% 20% 36% 20% 1	6699
	21st to end	Day	23% 9% 30% 25% 11% 2	6906
August	1st to 10th	Day	18% 8% 14% 46% 13% 1	4444
	11th to 20th	Day	37% 12% 24% 17% 8% 2	4195
	21st to end	Day	39% 10% 19% 21% 11% 1	4599
September	1st to 10th	Day	34% 11% 16% 25% 12% 3	2400
	11th to 20th	Day	44% 10% 14% 17% 14% 2	2370
	21st to end	Day	48% 10% 16% 15% 9% 1	2124
October	1st to 10th	Day	55% 9% 16% 15% 5%	3280
	11th to 20th	Day	59% 8% 11% 15% 6%	3261
	21st to end	Day	63% 10% 11% 12% 4	3258
November	1st to 10th	Day	68% 8% 10% 8% 5% 1	1648
	11th to 20th	Day	67% 8% 9% 9% 4 2	1680
	21st to end	Day	68% 7% 7% 11% 7% 1	1680
December	1st to 10th	Day	57% 9% 12% 17% 5% 1	2569
	11th to 20th	Day	77% 6% 8% 6% 2 1	2718
	21st to end	Day	79% 8% 6% 5% 2 1	3575
January	1st to 10th	Night	73% 6% 7% 10% 3	8770
	11th to 20th	Night	46% 7% 16% 19% 11% 1	8820
	21st to end	Night	61% 6% 10% 20% 3	9063
February	1st to 10th	Night	66% 7% 9% 10% 6% 2	2730
	11th to 20th	Night	60% 8% 10% 13% 8% 1	2664
	21st to end	Night	62% 7% 9% 13% 6% 2	2249
March	1st to 10th	Night	59% 9% 14% 12% 7%	5284
	11th to 20th	Night	57% 8% 11% 20% 4	5110
	21st to end	Night	69% 7% 11% 10% 2	5505
April	1st to 10th	Night	59% 9% 14% 15% 3	2100
	11th to 20th	Night	52% 8% 12% 15% 10% 2	1939
	21st to end	Night	52% 8% 14% 16% 9%	1848
May	1st to 10th	Night	35% 6% 17% 28% 14% 1	4721
	11th to 20th	Night	42% 10% 20% 23% 5%	4700
	21st to end	Night	48% 7% 22% 18% 4	4832
June	1st to 10th	Night	51% 7% 17% 16% 6% 3	1470
	11th to 20th	Night	47% 10% 17% 20% 7%	1470
	21st to end	Night	40% 10% 19% 20% 8% 3	1470
July	1st to 10th	Night	24% 8% 20% 26% 19% 4	3145
	11th to 20th	Night	12% 5% 22% 36% 22% 3	3138
	21st to end	Night	22% 7% 29% 27% 13% 2	3630
August	1st to 10th	Night	15% 5% 15% 41% 22% 2	2681
	11th to 20th	Night	33% 11% 27% 16% 9% 3	2929
	21st to end	Night	39% 8% 18% 24% 11% 1	3311
September	1st to 10th	Night	28% 9% 18% 28% 13% 5%	2000
	11th to 20th	Night	41% 9% 13% 18% 15% 4	2028
	21st to end	Night	48% 6% 15% 20% 8% 2	2276
October	1st to 10th	Night	51% 9% 18% 14% 7%	3920
	11th to 20th	Night	58% 6% 12% 18% 6%	3897
	21st to end	Night	60% 8% 11% 16% 5%	4541
November	1st to 10th	Night	70% 7% 10% 9% 4 1	2870
	11th to 20th	Night	66% 7% 10% 10% 6% 2	2940
	21st to end	Night	66% 7% 8% 11% 6% 1	2940
December	1st to 10th	Night	59% 8% 14% 15% 4 1	4826
	11th to 20th	Night	76% 7% 7% 6% 3	5706
	21st to end	Night	76% 7% 8% 7% 2	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	43% 10% 19% 16% 7% 4	220
	11th to 20th	Day	38% 12% 14% 20% 15% 1	220
	21st to end	Day	42% 8% 20% 18% 10% 2	286
February	1st to 10th	Day	36% 9% 25% 20% 10% 1	430
	11th to 20th	Day	33% 7% 25% 24% 9% 2	425
	21st to end	Day	30% 12% 25% 22% 10% 1	355
March	1st to 10th	Day	31% 10% 23% 24% 10% 2	538
	11th to 20th	Day	34% 10% 19% 23% 13% 2	540
	21st to end	Day	33% 10% 25% 21% 10% 1	594
April	1st to 10th	Day	29% 9% 22% 24% 14% 2	540
	11th to 20th	Day	24% 8% 27% 23% 16% 2	532
	21st to end	Day	22% 8% 27% 24% 16% 2	540
May	1st to 10th	Day	14% 7% 21% 36% 20% 2	543
	11th to 20th	Day	17% 6% 20% 30% 24% 3	568
	21st to end	Day	15% 6% 22% 32% 21% 4	730
June	1st to 10th	Day	19% 6% 22% 31% 20% 2	780
	11th to 20th	Day	15% 5% 24% 31% 21% 4	780
	21st to end	Day	15% 4 17% 34% 26% 4	780
July	1st to 10th	Day	12% 3 15% 34% 31% 5%	722
	11th to 20th	Day	7% 2 17% 39% 31% 5%	718
	21st to end	Day	6% 4 12% 32% 37% 8%	677
August	1st to 10th	Day	9% 2 13% 27% 37% 11%	527
	11th to 20th	Day	8% 4 11% 36% 33% 7%	517
	21st to end	Day	11% 5% 16% 37% 26% 4	583
September	1st to 10th	Day	14% 4 18% 34% 24% 5%	530
	11th to 20th	Day	22% 6% 18% 26% 22% 5%	530
	21st to end	Day	24% 7% 23% 26% 16% 4	530
October	1st to 10th	Day	28% 5% 19% 24% 18% 5%	530
	11th to 20th	Day	37% 7% 16% 19% 17% 4	530
	21st to end	Day	37% 12% 18% 21% 9% 3	437
November	1st to 10th	Day	37% 14% 23% 16% 11%	220
	11th to 20th	Day	41% 8% 12% 21% 13% 5%	220
	21st to end	Day	43% 13% 17% 11% 10% 6%	220
December	1st to 10th	Day	43% 5% 19% 15% 15% 5%	220
	11th to 20th	Day	43% 12% 19% 19% 6% 1	220
	21st to end	Day	44% 9% 25% 17% 4	242
January	1st to 10th	Night	47% 9% 19% 15% 10% 1	950
	11th to 20th	Night	40% 7% 16% 23% 14% 1	950
	21st to end	Night	39% 6% 18% 24% 12% 1	960
February	1st to 10th	Night	36% 7% 22% 24% 11%	840
	11th to 20th	Night	33% 7% 23% 26% 11% 1	824
	21st to end	Night	36% 10% 21% 20% 10% 3	692
March	1st to 10th	Night	33% 8% 20% 23% 14% 2	840
	11th to 20th	Night	37% 10% 17% 23% 13% 1	840
	21st to end	Night	36% 7% 19% 23% 13% 2	924
April	1st to 10th	Night	29% 8% 16% 27% 16% 4	840
	11th to 20th	Night	23% 7% 26% 27% 15% 2	691
	21st to end	Night	25% 6% 20% 30% 16% 3	588
May	1st to 10th	Night	16% 4 18% 32% 25% 5%	420
	11th to 20th	Night	17% 5% 11% 29% 30% 7%	414
	21st to end	Night	18% 4 14% 31% 29% 5%	455
June	1st to 10th	Night	23% 4 15% 31% 24% 4	420
	11th to 20th	Night	17% 5% 13% 33% 24% 7%	420
	21st to end	Night	12% 3 10% 32% 38% 5%	420
July	1st to 10th	Night	12% 2 9% 25% 42% 9%	390
	11th to 20th	Night	8% 2 7% 30% 42% 11%	388
	21st to end	Night	6% 1 7% 24% 50% 12%	438
August	1st to 10th	Night	8% 2 5% 22% 43% 20%	439
	11th to 20th	Night	8% 2 6% 27% 45% 12%	594
	21st to end	Night	12% 3 11% 28% 39% 7%	700
September	1st to 10th	Night	9% 3 12% 32% 33% 11%	800
	11th to 20th	Night	20% 4 14% 20% 30% 12%	800
	21st to end	Night	26% 6% 15% 26% 24% 4	800
October	1st to 10th	Night	23% 4 17% 30% 23% 3	800
	11th to 20th	Night	34% 5% 15% 27% 17% 3	800
	21st to end	Night	38% 8% 18% 24% 9% 2	880
November	1st to 10th	Night	42% 9% 19% 24% 6%	820
	11th to 20th	Night	41% 7% 21% 21% 9% 1	840
	21st to end	Night	43% 5% 20% 21% 10% 2	840
December	1st to 10th	Night	37% 7% 17% 27% 11% 1	879
	11th to 20th	Night	50% 7% 22% 15% 5%	950
	21st to end	Night	45% 10% 24% 16% 4	1045

Page generated at 2026-06-27 23:10:43. Version ac07

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