Prince George
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Prince George clear sky chart from 2005-11-06 to 2025-09-04.

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	10% 11% 4 9% 6% 6% 6% 5% 6% 7% 31%	130233
	Night	11% 13% 4 10% 6% 6% 6% 4 6% 7% 27%	127183
Transparency	Day	48% 10% 16% 19% 7%	129923
	Night	52% 9% 14% 17% 7% 1	127070
Seeing	Day	16% 10% 23% 26% 19% 6%	17575
	Night	19% 8% 20% 31% 18% 3	25281

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	8% 20% 8% 16% 8% 6% 5% 4 4 5% 17%	2967
	11th to 20th	Day	10% 14% 5% 9% 5% 5% 5% 5% 6% 6% 30%	3159
	21st to end	Day	10% 21% 6% 11% 6% 5% 5% 4 5% 6% 21%	3498
February	1st to 10th	Day	14% 16% 5% 10% 7% 4 4 3 6% 6% 24%	1616
	11th to 20th	Day	11% 14% 5% 11% 7% 6% 5% 4 6% 7% 24%	1755
	21st to end	Day	6% 17% 5% 10% 8% 5% 5% 3 6% 6% 28%	1485
March	1st to 10th	Day	6% 14% 5% 14% 8% 6% 6% 4 6% 8% 23%	4496
	11th to 20th	Day	5% 11% 4 9% 7% 7% 7% 6% 9% 9% 25%	5000
	21st to end	Day	8% 14% 4 8% 5% 5% 5% 4 6% 6% 35%	5699
April	1st to 10th	Day	7% 11% 5% 12% 8% 6% 6% 5% 7% 7% 26%	2400
	11th to 20th	Day	10% 13% 4 9% 7% 7% 6% 5% 6% 6% 26%	2556
	21st to end	Day	12% 12% 4 9% 6% 6% 5% 4 6% 7% 30%	2789
May	1st to 10th	Day	7% 9% 4 10% 6% 5% 6% 5% 7% 9% 32%	6320
	11th to 20th	Day	10% 11% 5% 13% 8% 7% 6% 6% 7% 7% 21%	6566
	21st to end	Day	10% 10% 4 10% 8% 7% 8% 6% 7% 8% 22%	7762
June	1st to 10th	Day	11% 8% 3 9% 7% 6% 7% 5% 7% 8% 31%	3200
	11th to 20th	Day	14% 8% 3 8% 7% 7% 6% 5% 7% 9% 27%	3200
	21st to end	Day	10% 8% 4 8% 6% 5% 6% 6% 7% 7% 32%	3200
July	1st to 10th	Day	9% 7% 2 6% 5% 4 5% 4 6% 8% 43%	7240
	11th to 20th	Day	9% 7% 2 6% 4 4 5% 4 6% 8% 45%	6830
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 6% 7% 10% 40%	7375
August	1st to 10th	Day	4 4 1 4 3 4 4 3 6% 9% 58%	4649
	11th to 20th	Day	8% 5% 2 7% 5% 5% 5% 5% 7% 9% 42%	4393
	21st to end	Day	11% 8% 3 9% 5% 6% 5% 5% 6% 7% 35%	4664
September	1st to 10th	Day	10% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	2319
	11th to 20th	Day	10% 6% 3 8% 5% 6% 6% 5% 7% 8% 37%	2280
	21st to end	Day	16% 9% 3 9% 7% 5% 6% 4 6% 7% 28%	2003
October	1st to 10th	Day	16% 13% 4 10% 6% 6% 5% 4 5% 6% 24%	3180
	11th to 20th	Day	17% 13% 3 9% 5% 6% 6% 4 6% 7% 25%	3140
	21st to end	Day	12% 11% 4 9% 6% 5% 6% 4 6% 8% 30%	2854
November	1st to 10th	Day	19% 15% 5% 11% 5% 4 4 4 5% 4 24%	1568
	11th to 20th	Day	11% 18% 5% 12% 9% 6% 6% 4 6% 6% 17%	1587
	21st to end	Day	14% 20% 5% 10% 7% 6% 5% 7% 5% 4 17%	1269
December	1st to 10th	Day	21% 19% 5% 10% 7% 6% 5% 4 4 4 14%	1960
	11th to 20th	Day	14% 22% 7% 14% 9% 6% 5% 4 3 4 12%	2262
	21st to end	Day	6% 19% 6% 13% 7% 7% 6% 4 6% 6% 19%	2992
January	1st to 10th	Night	10% 18% 7% 14% 7% 7% 7% 5% 5% 4 16%	7020
	11th to 20th	Night	11% 14% 4 9% 6% 6% 6% 4 5% 7% 29%	6739
	21st to end	Night	17% 21% 5% 9% 5% 4 5% 4 7% 7% 16%	7458
February	1st to 10th	Night	14% 19% 5% 9% 7% 5% 5% 4 5% 5% 23%	2782
	11th to 20th	Night	11% 14% 5% 10% 8% 5% 5% 4 5% 7% 25%	2532
	21st to end	Night	8% 15% 5% 11% 6% 5% 5% 4 6% 6% 29%	2145
March	1st to 10th	Night	6% 16% 5% 12% 6% 6% 6% 5% 6% 9% 24%	5394
	11th to 20th	Night	6% 12% 5% 11% 7% 7% 6% 5% 8% 7% 26%	4999
	21st to end	Night	10% 11% 3 7% 4 4 5% 4 6% 6% 39%	5275
April	1st to 10th	Night	9% 13% 4 9% 7% 6% 6% 5% 6% 8% 29%	2000
	11th to 20th	Night	9% 12% 3 8% 6% 7% 7% 5% 7% 8% 29%	1791
	21st to end	Night	11% 10% 4 8% 5% 6% 6% 5% 6% 7% 33%	1610
May	1st to 10th	Night	12% 10% 3 9% 5% 5% 6% 5% 7% 8% 30%	3640
	11th to 20th	Night	12% 11% 4 10% 6% 6% 6% 5% 7% 10% 24%	3325
	21st to end	Night	11% 12% 4 12% 7% 6% 6% 4 6% 6% 25%	3110
June	1st to 10th	Night	13% 9% 3 7% 6% 6% 7% 3 8% 7% 30%	1200
	11th to 20th	Night	14% 10% 3 8% 6% 5% 6% 5% 8% 7% 28%	1200
	21st to end	Night	10% 7% 3 9% 7% 7% 8% 5% 8% 8% 28%	1200
July	1st to 10th	Night	7% 7% 3 7% 5% 5% 5% 4 6% 8% 44%	2720
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 6% 7% 49%	3126
	21st to end	Night	10% 5% 2 6% 4 4 6% 4 8% 10% 41%	3468
August	1st to 10th	Night	4 3 1 3 3 2 3 3 5% 7% 67%	2501
	11th to 20th	Night	7% 5% 2 5% 4 5% 5% 4 6% 9% 48%	2642
	21st to end	Night	13% 7% 3 8% 5% 5% 5% 5% 6% 7% 36%	3245
September	1st to 10th	Night	12% 7% 3 7% 5% 5% 4 3 6% 8% 40%	1928
	11th to 20th	Night	10% 8% 3 6% 4 5% 5% 4 5% 8% 42%	1900
	21st to end	Night	16% 11% 4 8% 5% 4 5% 4 6% 6% 32%	2175
October	1st to 10th	Night	17% 14% 4 9% 6% 5% 5% 4 6% 7% 24%	3800
	11th to 20th	Night	12% 11% 4 9% 6% 6% 6% 4 7% 7% 28%	3797
	21st to end	Night	12% 12% 4 9% 5% 6% 6% 5% 5% 7% 28%	4696
November	1st to 10th	Night	17% 15% 4 8% 6% 6% 6% 5% 6% 5% 22%	2730
	11th to 20th	Night	12% 16% 5% 11% 8% 6% 6% 4 6% 6% 20%	2800
	21st to end	Night	12% 21% 5% 11% 6% 5% 6% 4 6% 6% 19%	3121
December	1st to 10th	Night	16% 18% 4 10% 6% 8% 7% 4 5% 5% 17%	5220
	11th to 20th	Night	16% 21% 5% 12% 8% 6% 5% 3 5% 5% 14%	5930
	21st to end	Night	6% 18% 6% 13% 8% 7% 6% 4 6% 6% 19%	7964

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	63% 12% 10% 11% 4	2967
	11th to 20th	Day	52% 8% 14% 15% 8% 3	3180
	21st to end	Day	61% 11% 13% 12% 3	3498
February	1st to 10th	Day	57% 10% 11% 10% 11%	1616
	11th to 20th	Day	58% 10% 15% 14% 4	1764
	21st to end	Day	55% 9% 13% 14% 8% 2	1485
March	1st to 10th	Day	53% 9% 12% 17% 9%	4496
	11th to 20th	Day	46% 13% 15% 18% 8% 1	5000
	21st to end	Day	47% 8% 13% 21% 11%	5699
April	1st to 10th	Day	53% 12% 12% 18% 6% 1	2400
	11th to 20th	Day	55% 8% 11% 19% 7%	2556
	21st to end	Day	51% 9% 15% 18% 7%	2789
May	1st to 10th	Day	43% 9% 17% 21% 9% 1	6320
	11th to 20th	Day	52% 12% 15% 15% 7%	6569
	21st to end	Day	52% 12% 15% 16% 4 1	7763
June	1st to 10th	Day	47% 11% 13% 19% 9%	3200
	11th to 20th	Day	49% 11% 16% 19% 4	3200
	21st to end	Day	45% 12% 17% 20% 6%	3200
July	1st to 10th	Day	36% 7% 14% 23% 19% 1	7161
	11th to 20th	Day	36% 7% 20% 28% 9%	6747
	21st to end	Day	34% 9% 22% 26% 9%	7168
August	1st to 10th	Day	22% 8% 20% 36% 13% 1	4631
	11th to 20th	Day	35% 9% 21% 27% 7%	4435
	21st to end	Day	45% 9% 24% 19% 3	4663
September	1st to 10th	Day	40% 11% 23% 21% 5%	2319
	11th to 20th	Day	41% 10% 19% 24% 5%	2280
	21st to end	Day	52% 11% 15% 17% 4 1	2003
October	1st to 10th	Day	56% 9% 19% 12% 5%	3180
	11th to 20th	Day	55% 9% 18% 16% 1	3140
	21st to end	Day	49% 11% 23% 11% 5%	2854
November	1st to 10th	Day	60% 9% 12% 13% 5%	1568
	11th to 20th	Day	64% 13% 10% 10% 4	1587
	21st to end	Day	67% 11% 10% 10% 2	1269
December	1st to 10th	Day	71% 10% 10% 7% 2	1960
	11th to 20th	Day	73% 11% 7% 6% 4	2264
	21st to end	Day	60% 9% 14% 12% 4	2992
January	1st to 10th	Night	62% 12% 11% 10% 4	7020
	11th to 20th	Night	53% 9% 13% 11% 9% 4	6780
	21st to end	Night	63% 9% 16% 10% 2	7458
February	1st to 10th	Night	62% 7% 11% 10% 9% 1	2782
	11th to 20th	Night	57% 9% 15% 14% 5%	2534
	21st to end	Night	53% 9% 13% 16% 8% 1	2145
March	1st to 10th	Night	52% 10% 11% 16% 10%	5394
	11th to 20th	Night	47% 11% 11% 22% 9%	5000
	21st to end	Night	42% 8% 13% 23% 14%	5275
April	1st to 10th	Night	51% 9% 13% 19% 7%	2000
	11th to 20th	Night	51% 8% 13% 19% 9%	1791
	21st to end	Night	48% 9% 12% 20% 10%	1610
May	1st to 10th	Night	46% 10% 13% 22% 8% 1	3637
	11th to 20th	Night	48% 12% 15% 20% 4	3325
	21st to end	Night	55% 9% 11% 20% 4 1	3110
June	1st to 10th	Night	48% 11% 12% 19% 10% 1	1200
	11th to 20th	Night	52% 11% 12% 20% 6%	1200
	21st to end	Night	49% 11% 17% 19% 4	1200
July	1st to 10th	Night	36% 8% 13% 23% 19% 1	2690
	11th to 20th	Night	33% 7% 18% 35% 7%	3086
	21st to end	Night	33% 10% 24% 22% 11%	3370
August	1st to 10th	Night	18% 6% 17% 40% 17% 1	2494
	11th to 20th	Night	31% 9% 18% 34% 8%	2666
	21st to end	Night	46% 8% 23% 18% 4	3245
September	1st to 10th	Night	40% 9% 19% 24% 7% 1	1928
	11th to 20th	Night	39% 10% 14% 28% 8%	1900
	21st to end	Night	51% 9% 14% 18% 8%	2175
October	1st to 10th	Night	57% 8% 15% 16% 4	3800
	11th to 20th	Night	50% 9% 19% 18% 4	3797
	21st to end	Night	53% 10% 18% 15% 4	4696
November	1st to 10th	Night	61% 9% 12% 13% 5%	2730
	11th to 20th	Night	61% 10% 11% 13% 5%	2800
	21st to end	Night	62% 11% 12% 12% 3	3121
December	1st to 10th	Night	65% 11% 12% 10% 3	5220
	11th to 20th	Night	70% 9% 11% 7% 3	5927
	21st to end	Night	60% 11% 13% 12% 4	7964

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	15% 8% 22% 33% 17% 7%	200
	11th to 20th	Day	19% 13% 20% 27% 18% 4	200
	21st to end	Day	23% 13% 22% 22% 16% 4	220
February	1st to 10th	Day	21% 18% 25% 17% 14% 5%	249
	11th to 20th	Day	18% 11% 25% 24% 18% 3	395
	21st to end	Day	14% 18% 31% 22% 11% 5%	331
March	1st to 10th	Day	14% 17% 23% 23% 17% 6%	486
	11th to 20th	Day	16% 14% 28% 23% 16% 3	500
	21st to end	Day	17% 17% 26% 18% 15% 7%	550
April	1st to 10th	Day	14% 16% 26% 28% 13% 3	500
	11th to 20th	Day	16% 14% 28% 23% 13% 5%	492
	21st to end	Day	16% 15% 27% 26% 13% 4	500
May	1st to 10th	Day	15% 15% 28% 24% 15% 3	503
	11th to 20th	Day	12% 10% 23% 30% 20% 5%	646
	21st to end	Day	14% 8% 24% 26% 23% 5%	939
June	1st to 10th	Day	15% 10% 25% 29% 19% 2	930
	11th to 20th	Day	16% 8% 23% 28% 20% 5%	930
	21st to end	Day	12% 6% 25% 29% 24% 6%	930
July	1st to 10th	Day	15% 6% 18% 30% 24% 8%	916
	11th to 20th	Day	16% 6% 19% 26% 26% 7%	740
	21st to end	Day	10% 7% 17% 29% 29% 8%	794
August	1st to 10th	Day	9% 6% 16% 30% 28% 10%	597
	11th to 20th	Day	10% 6% 25% 29% 20% 9%	517
	21st to end	Day	13% 8% 26% 25% 19% 9%	583
September	1st to 10th	Day	15% 7% 24% 23% 24% 7%	503
	11th to 20th	Day	15% 8% 21% 26% 23% 7%	490
	21st to end	Day	20% 14% 29% 20% 13% 4	490
October	1st to 10th	Day	22% 12% 22% 23% 15% 6%	490
	11th to 20th	Day	22% 11% 26% 22% 16% 3	481
	21st to end	Day	20% 13% 26% 25% 13% 3	253
November	1st to 10th	Day	34% 11% 21% 20% 10% 5%	200
	11th to 20th	Day	24% 11% 23% 20% 18% 6%	200
	21st to end	Day	24% 11% 25% 26% 11% 4	200
December	1st to 10th	Day	19% 8% 21% 28% 20% 5%	200
	11th to 20th	Day	15% 10% 20% 34% 18% 4	200
	21st to end	Day	23% 7% 15% 34% 15% 6%	220
January	1st to 10th	Night	24% 9% 24% 30% 11% 2	1011
	11th to 20th	Night	24% 9% 25% 26% 15% 1	900
	21st to end	Night	24% 13% 23% 26% 13% 2	990
February	1st to 10th	Night	25% 12% 18% 26% 15% 3	815
	11th to 20th	Night	20% 9% 22% 33% 16% 2	784
	21st to end	Night	17% 11% 22% 32% 15% 3	660
March	1st to 10th	Night	18% 10% 22% 31% 16% 3	800
	11th to 20th	Night	15% 12% 24% 32% 15% 2	800
	21st to end	Night	15% 9% 18% 29% 24% 5%	880
April	1st to 10th	Night	18% 8% 20% 31% 21% 3	800
	11th to 20th	Night	15% 7% 23% 32% 19% 5%	603
	21st to end	Night	16% 7% 24% 31% 20% 1	410
May	1st to 10th	Night	17% 7% 22% 35% 17% 4	400
	11th to 20th	Night	14% 3 18% 37% 25% 3	394
	21st to end	Night	15% 6% 21% 32% 25% 2	433
June	1st to 10th	Night	16% 5% 21% 35% 20% 3	400
	11th to 20th	Night	19% 4 22% 28% 24% 4	400
	21st to end	Night	12% 5% 18% 33% 30% 3	400
July	1st to 10th	Night	13% 2 16% 38% 31% 1	390
	11th to 20th	Night	13% 3 15% 35% 30% 4	388
	21st to end	Night	13% 3 13% 35% 31% 6%	438
August	1st to 10th	Night	8% 4 10% 34% 37% 7%	398
	11th to 20th	Night	9% 2 17% 36% 31% 6%	435
	21st to end	Night	19% 3 13% 32% 28% 4	660
September	1st to 10th	Night	16% 4 15% 34% 27% 3	770
	11th to 20th	Night	14% 5% 13% 32% 30% 6%	760
	21st to end	Night	21% 10% 21% 28% 17% 2	760
October	1st to 10th	Night	21% 8% 17% 31% 19% 4	760
	11th to 20th	Night	22% 7% 24% 29% 17% 2	760
	21st to end	Night	24% 11% 24% 30% 11%	836
November	1st to 10th	Night	27% 13% 20% 28% 11% 2	780
	11th to 20th	Night	24% 13% 24% 27% 11% 2	800
	21st to end	Night	26% 12% 23% 28% 9% 2	1056
December	1st to 10th	Night	21% 8% 19% 33% 17% 2	1100
	11th to 20th	Night	25% 9% 21% 30% 13% 2	1100
	21st to end	Night	20% 9% 24% 30% 14% 2	1210

Page generated at 2025-08-31 22:51:08. Version ac07

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