Vanderhoof
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vanderhoof clear sky chart from 2005-11-06 to 2024-02-15.

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	12% 11% 4 8% 7% 4 6% 5% 6% 7% 30%	77435
	Night	13% 13% 5% 9% 7% 4 6% 5% 6% 6% 26%	81569
Transparency	Day	52% 9% 15% 17% 6% 1	77132
	Night	56% 9% 14% 15% 6% 1	81452
Seeing	Day	18% 12% 26% 26% 15% 4	15315
	Night	19% 11% 25% 28% 16% 2	23340

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	9% 18% 6% 12% 12% 6% 7% 5% 5% 5% 15%	2169
	11th to 20th	Day	11% 16% 6% 8% 7% 4 4 5% 6% 7% 26%	2199
	21st to end	Day	12% 24% 6% 11% 10% 5% 4 4 4 6% 15%	2442
February	1st to 10th	Day	14% 15% 5% 9% 8% 5% 5% 4 6% 5% 25%	1522
	11th to 20th	Day	10% 15% 6% 9% 7% 4 5% 5% 5% 7% 26%	1612
	21st to end	Day	7% 14% 8% 11% 8% 3 5% 5% 5% 6% 29%	1332
March	1st to 10th	Day	9% 13% 5% 7% 8% 4 6% 6% 6% 6% 30%	1787
	11th to 20th	Day	8% 14% 6% 8% 7% 5% 5% 6% 7% 7% 27%	1980
	21st to end	Day	9% 13% 5% 8% 8% 4 7% 6% 6% 7% 27%	2225
April	1st to 10th	Day	9% 13% 6% 10% 9% 5% 5% 5% 6% 6% 25%	2200
	11th to 20th	Day	12% 13% 6% 9% 7% 4 6% 5% 5% 6% 27%	2308
	21st to end	Day	14% 13% 5% 8% 7% 4 6% 6% 5% 7% 27%	2470
May	1st to 10th	Day	12% 13% 5% 9% 8% 3 6% 6% 5% 6% 29%	2520
	11th to 20th	Day	12% 9% 3 7% 7% 5% 6% 6% 6% 8% 31%	2642
	21st to end	Day	12% 8% 3 8% 8% 4 7% 6% 6% 7% 30%	2984
June	1st to 10th	Day	12% 7% 4 8% 8% 5% 6% 6% 6% 8% 29%	2880
	11th to 20th	Day	15% 7% 4 7% 8% 4 7% 5% 6% 7% 29%	2880
	21st to end	Day	11% 7% 3 6% 7% 5% 6% 6% 6% 8% 35%	2880
July	1st to 10th	Day	13% 7% 3 6% 6% 5% 6% 5% 7% 8% 35%	2831
	11th to 20th	Day	13% 6% 3 6% 5% 4 5% 5% 7% 8% 38%	2700
	21st to end	Day	9% 5% 2 7% 6% 3 7% 6% 7% 8% 41%	2938
August	1st to 10th	Day	7% 6% 3 5% 5% 3 5% 5% 7% 8% 47%	2620
	11th to 20th	Day	8% 5% 2 4 5% 3 5% 5% 6% 9% 46%	2390
	21st to end	Day	13% 6% 4 7% 7% 5% 5% 6% 6% 8% 32%	2574
September	1st to 10th	Day	13% 6% 2 6% 6% 3 5% 6% 7% 7% 37%	2201
	11th to 20th	Day	12% 7% 4 6% 7% 4 5% 5% 6% 8% 37%	2125
	21st to end	Day	17% 10% 4 7% 6% 3 5% 5% 7% 8% 28%	1918
October	1st to 10th	Day	16% 10% 4 8% 6% 5% 5% 5% 5% 8% 29%	1800
	11th to 20th	Day	14% 13% 4 7% 6% 3 6% 6% 6% 8% 27%	1800
	21st to end	Day	15% 14% 5% 8% 5% 3 5% 5% 4 7% 28%	1624
November	1st to 10th	Day	20% 15% 3 8% 6% 3 5% 4 5% 6% 24%	1488
	11th to 20th	Day	13% 16% 6% 11% 7% 4 6% 6% 6% 7% 18%	1520
	21st to end	Day	14% 17% 7% 10% 7% 6% 6% 5% 6% 5% 17%	1202
December	1st to 10th	Day	13% 12% 5% 9% 9% 5% 7% 5% 8% 8% 20%	1140
	11th to 20th	Day	17% 17% 5% 11% 8% 4 6% 5% 5% 5% 18%	1442
	21st to end	Day	9% 16% 6% 10% 7% 4 6% 6% 6% 5% 23%	2090
January	1st to 10th	Night	9% 17% 7% 12% 9% 5% 7% 6% 6% 6% 15%	4790
	11th to 20th	Night	11% 14% 6% 10% 8% 4 5% 5% 4 5% 27%	4699
	21st to end	Night	17% 19% 6% 9% 8% 4 6% 5% 5% 6% 14%	5214
February	1st to 10th	Night	15% 17% 6% 10% 8% 4 5% 4 5% 4 24%	2655
	11th to 20th	Night	12% 14% 6% 8% 8% 4 5% 5% 5% 7% 25%	2329
	21st to end	Night	10% 13% 6% 10% 8% 4 4 5% 5% 6% 30%	1924
March	1st to 10th	Night	8% 15% 5% 10% 7% 3 6% 5% 5% 7% 28%	2170
	11th to 20th	Night	8% 12% 6% 9% 9% 5% 6% 6% 6% 6% 28%	1979
	21st to end	Night	8% 13% 4 10% 8% 4 7% 6% 6% 6% 27%	2130
April	1st to 10th	Night	8% 13% 5% 10% 7% 5% 6% 6% 6% 7% 28%	1759
	11th to 20th	Night	9% 10% 5% 9% 7% 5% 7% 6% 7% 7% 27%	1601
	21st to end	Night	10% 13% 4 7% 6% 3 5% 5% 6% 7% 34%	1490
May	1st to 10th	Night	15% 10% 5% 9% 8% 5% 5% 6% 5% 6% 26%	1440
	11th to 20th	Night	12% 9% 5% 7% 7% 3 6% 6% 7% 7% 31%	1249
	21st to end	Night	17% 9% 4 7% 8% 4 6% 5% 6% 8% 26%	1289
June	1st to 10th	Night	15% 9% 4 7% 7% 5% 7% 6% 7% 5% 29%	1080
	11th to 20th	Night	14% 8% 4 7% 8% 4 6% 6% 7% 6% 28%	1080
	21st to end	Night	11% 6% 4 7% 5% 4 7% 7% 8% 10% 32%	1080
July	1st to 10th	Night	13% 8% 3 8% 7% 4 6% 6% 6% 8% 32%	1125
	11th to 20th	Night	14% 5% 2 6% 7% 4 6% 5% 7% 8% 37%	1260
	21st to end	Night	12% 4 2 6% 5% 4 5% 6% 5% 6% 44%	1379
August	1st to 10th	Night	8% 6% 2 3 5% 2 4 6% 7% 8% 49%	1318
	11th to 20th	Night	9% 6% 2 4 5% 3 4 6% 5% 8% 48%	1507
	21st to end	Night	15% 7% 4 7% 8% 4 6% 6% 7% 7% 30%	1782
September	1st to 10th	Night	14% 8% 3 7% 6% 3 5% 4 6% 7% 37%	1759
	11th to 20th	Night	11% 8% 3 6% 6% 3 4 6% 4 7% 41%	1831
	21st to end	Night	17% 9% 4 7% 6% 4 5% 5% 5% 8% 31%	2042
October	1st to 10th	Night	16% 10% 4 8% 6% 3 4 6% 6% 6% 31%	2160
	11th to 20th	Night	19% 11% 4 8% 6% 4 6% 5% 5% 6% 27%	2160
	21st to end	Night	16% 13% 4 7% 6% 4 5% 5% 5% 6% 28%	2730
November	1st to 10th	Night	18% 14% 5% 7% 6% 5% 5% 5% 5% 7% 22%	2590
	11th to 20th	Night	13% 17% 5% 10% 8% 4 5% 5% 5% 6% 21%	2660
	21st to end	Night	11% 19% 6% 11% 7% 5% 5% 5% 5% 6% 21%	2952
December	1st to 10th	Night	13% 13% 5% 9% 8% 4 6% 5% 6% 5% 26%	3040
	11th to 20th	Night	18% 18% 6% 9% 7% 4 5% 5% 5% 6% 19%	3750
	21st to end	Night	9% 16% 6% 10% 9% 5% 6% 6% 5% 6% 21%	5566

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	62% 14% 12% 10% 2	2169
	11th to 20th	Day	57% 8% 13% 7% 10% 5%	2220
	21st to end	Day	70% 8% 8% 9% 4	2442
February	1st to 10th	Day	59% 7% 13% 10% 9% 2	1522
	11th to 20th	Day	56% 9% 16% 14% 4 1	1621
	21st to end	Day	56% 7% 13% 15% 7% 3	1332
March	1st to 10th	Day	52% 8% 13% 18% 9% 1	1787
	11th to 20th	Day	53% 9% 15% 15% 6%	1980
	21st to end	Day	56% 8% 16% 16% 4	2225
April	1st to 10th	Day	59% 8% 11% 17% 5%	2200
	11th to 20th	Day	59% 7% 11% 17% 6%	2308
	21st to end	Day	56% 7% 12% 17% 8%	2470
May	1st to 10th	Day	56% 7% 13% 17% 7% 1	2520
	11th to 20th	Day	50% 9% 13% 18% 9% 1	2645
	21st to end	Day	53% 8% 15% 17% 7% 1	2985
June	1st to 10th	Day	52% 8% 15% 17% 7% 1	2880
	11th to 20th	Day	52% 10% 14% 18% 5%	2880
	21st to end	Day	46% 10% 16% 21% 7%	2880
July	1st to 10th	Day	47% 10% 15% 21% 7% 1	2754
	11th to 20th	Day	44% 9% 19% 23% 5%	2619
	21st to end	Day	38% 11% 21% 22% 8%	2775
August	1st to 10th	Day	35% 10% 23% 26% 6%	2602
	11th to 20th	Day	34% 11% 22% 27% 6%	2390
	21st to end	Day	48% 11% 18% 19% 3	2574
September	1st to 10th	Day	43% 11% 22% 19% 5%	2201
	11th to 20th	Day	44% 10% 17% 24% 6%	2125
	21st to end	Day	53% 10% 16% 16% 4 1	1918
October	1st to 10th	Day	53% 11% 17% 16% 4	1800
	11th to 20th	Day	54% 12% 16% 16% 2	1800
	21st to end	Day	55% 9% 15% 17% 4	1624
November	1st to 10th	Day	60% 9% 13% 12% 5%	1488
	11th to 20th	Day	63% 11% 13% 9% 4	1520
	21st to end	Day	67% 8% 11% 11% 3	1202
December	1st to 10th	Day	55% 14% 14% 13% 4	1140
	11th to 20th	Day	68% 9% 10% 10% 4	1444
	21st to end	Day	55% 11% 14% 14% 7%	2090
January	1st to 10th	Night	62% 12% 12% 11% 2	4790
	11th to 20th	Night	58% 8% 11% 6% 11% 6%	4740
	21st to end	Night	69% 12% 8% 7% 4	5214
February	1st to 10th	Night	63% 7% 10% 11% 9% 1	2655
	11th to 20th	Night	58% 6% 15% 14% 6%	2331
	21st to end	Night	54% 7% 12% 18% 7% 2	1924
March	1st to 10th	Night	54% 7% 15% 14% 8% 1	2170
	11th to 20th	Night	54% 8% 12% 19% 7%	1980
	21st to end	Night	54% 9% 14% 17% 5%	2130
April	1st to 10th	Night	54% 9% 14% 16% 7%	1759
	11th to 20th	Night	53% 9% 13% 19% 6%	1601
	21st to end	Night	49% 7% 13% 21% 10%	1490
May	1st to 10th	Night	55% 9% 14% 16% 6%	1440
	11th to 20th	Night	49% 8% 15% 19% 8% 1	1249
	21st to end	Night	53% 11% 12% 17% 6%	1289
June	1st to 10th	Night	51% 12% 11% 17% 8% 1	1080
	11th to 20th	Night	53% 8% 15% 18% 7%	1080
	21st to end	Night	45% 11% 18% 20% 6%	1080
July	1st to 10th	Night	48% 9% 15% 19% 8%	1093
	11th to 20th	Night	44% 10% 19% 22% 5% 1	1218
	21st to end	Night	36% 11% 21% 23% 9%	1302
August	1st to 10th	Night	31% 10% 23% 27% 9%	1311
	11th to 20th	Night	34% 10% 20% 29% 8%	1507
	21st to end	Night	50% 11% 17% 17% 4 1	1782
September	1st to 10th	Night	45% 10% 17% 22% 5% 1	1759
	11th to 20th	Night	40% 8% 15% 27% 9% 1	1831
	21st to end	Night	52% 8% 14% 19% 6%	2042
October	1st to 10th	Night	50% 10% 17% 18% 5%	2160
	11th to 20th	Night	57% 8% 16% 15% 4	2160
	21st to end	Night	54% 9% 15% 17% 5%	2730
November	1st to 10th	Night	61% 9% 12% 13% 5%	2590
	11th to 20th	Night	61% 9% 14% 10% 5%	2660
	21st to end	Night	62% 9% 13% 10% 5%	2952
December	1st to 10th	Night	57% 9% 14% 16% 4	3040
	11th to 20th	Night	65% 11% 11% 9% 4	3747
	21st to end	Night	59% 10% 12% 13% 6%	5566

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	18% 9% 32% 22% 15% 4	180
	11th to 20th	Day	21% 16% 26% 21% 15% 2	180
	21st to end	Day	20% 19% 27% 22% 8% 5%	198
February	1st to 10th	Day	25% 16% 29% 17% 9% 3	270
	11th to 20th	Day	18% 13% 33% 27% 8% 1	348
	21st to end	Day	17% 15% 34% 20% 10% 3	280
March	1st to 10th	Day	13% 17% 27% 25% 16% 2	390
	11th to 20th	Day	18% 16% 30% 24% 12% 1	420
	21st to end	Day	20% 17% 24% 22% 10% 6%	462
April	1st to 10th	Day	17% 18% 31% 23% 8% 4	420
	11th to 20th	Day	19% 17% 24% 19% 12% 8%	412
	21st to end	Day	20% 14% 30% 22% 12% 3	420
May	1st to 10th	Day	17% 15% 29% 23% 13% 4	423
	11th to 20th	Day	16% 11% 27% 26% 16% 5%	611
	21st to end	Day	16% 12% 23% 29% 16% 3	747
June	1st to 10th	Day	15% 14% 27% 27% 14% 3	810
	11th to 20th	Day	18% 10% 26% 30% 12% 3	810
	21st to end	Day	13% 8% 28% 30% 17% 5%	810
July	1st to 10th	Day	16% 7% 23% 27% 23% 4	749
	11th to 20th	Day	17% 10% 23% 28% 20% 3	618
	21st to end	Day	11% 7% 23% 36% 18% 4	684
August	1st to 10th	Day	8% 7% 20% 33% 25% 7%	560
	11th to 20th	Day	11% 11% 22% 28% 20% 8%	437
	21st to end	Day	17% 11% 26% 26% 15% 5%	495
September	1st to 10th	Day	19% 10% 25% 24% 17% 4	450
	11th to 20th	Day	16% 10% 24% 23% 20% 6%	450
	21st to end	Day	25% 15% 28% 18% 13% 1	450
October	1st to 10th	Day	25% 12% 21% 24% 13% 5%	450
	11th to 20th	Day	25% 13% 28% 20% 12% 2	450
	21st to end	Day	22% 12% 30% 24% 8% 3	233
November	1st to 10th	Day	35% 13% 18% 22% 9% 2	180
	11th to 20th	Day	25% 14% 24% 16% 16% 4	180
	21st to end	Day	24% 14% 26% 21% 10% 5%	180
December	1st to 10th	Day	18% 9% 22% 32% 16% 4	180
	11th to 20th	Day	15% 12% 24% 32% 14% 3	180
	21st to end	Day	23% 8% 25% 24% 14% 6%	198
January	1st to 10th	Night	22% 16% 27% 26% 8% 2	888
	11th to 20th	Night	21% 14% 28% 25% 12% 1	850
	21st to end	Night	20% 15% 27% 26% 12% 1	935
February	1st to 10th	Night	24% 12% 24% 25% 12% 2	801
	11th to 20th	Night	20% 9% 29% 28% 13% 1	722
	21st to end	Night	15% 11% 28% 28% 15% 3	592
March	1st to 10th	Night	17% 14% 25% 27% 15% 3	720
	11th to 20th	Night	15% 13% 28% 28% 14% 1	720
	21st to end	Night	14% 12% 20% 28% 23% 4	792
April	1st to 10th	Night	15% 9% 23% 30% 19% 3	679
	11th to 20th	Night	13% 9% 27% 29% 19% 4	533
	21st to end	Night	16% 11% 29% 28% 16% 1	410
May	1st to 10th	Night	16% 10% 25% 32% 16% 1	360
	11th to 20th	Night	14% 5% 26% 34% 19% 1	354
	21st to end	Night	19% 7% 26% 26% 21% 2	389
June	1st to 10th	Night	18% 8% 24% 34% 16% 1	360
	11th to 20th	Night	17% 7% 28% 28% 19% 1	360
	21st to end	Night	14% 6% 24% 34% 20% 2	360
July	1st to 10th	Night	15% 7% 23% 33% 22% 1	350
	11th to 20th	Night	16% 6% 24% 28% 24% 3	348
	21st to end	Night	13% 6% 22% 30% 23% 4	394
August	1st to 10th	Night	10% 4 19% 30% 31% 6%	358
	11th to 20th	Night	10% 4 20% 35% 27% 3	439
	21st to end	Night	18% 4 23% 32% 20% 3	594
September	1st to 10th	Night	16% 5% 22% 31% 24% 2	679
	11th to 20th	Night	14% 7% 18% 30% 27% 5%	720
	21st to end	Night	21% 11% 26% 26% 15% 1	720
October	1st to 10th	Night	21% 9% 20% 29% 17% 3	720
	11th to 20th	Night	27% 9% 21% 28% 14% 2	720
	21st to end	Night	26% 11% 27% 26% 10% 1	792
November	1st to 10th	Night	26% 15% 24% 24% 8% 2	740
	11th to 20th	Night	23% 15% 29% 23% 10% 1	760
	21st to end	Night	24% 13% 27% 25% 9% 1	957
December	1st to 10th	Night	19% 10% 23% 32% 13% 2	1040
	11th to 20th	Night	21% 13% 26% 27% 11% 1	1040
	21st to end	Night	20% 13% 27% 27% 13% 1	1144

Page generated at 2024-02-12 03:35:31. Version ac07

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