Vernon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vernon clear sky chart from 2005-11-06 to 2024-01-12.

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 6% 6% 6% 8% 35%	74772
	Night	9% 10% 4 8% 8% 4 6% 5% 6% 7% 32%	74911
Transparency	Day	46% 12% 16% 17% 8% 1	74464
	Night	49% 12% 15% 16% 7% 1	74737
Seeing	Day	13% 13% 26% 27% 16% 4	14344
	Night	15% 8% 23% 32% 19% 3	22968

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	14% 15% 6% 9% 8% 6% 8% 6% 6% 7% 15%	1389
	11th to 20th	Day	9% 12% 5% 11% 9% 6% 7% 8% 6% 6% 21%	1451
	21st to end	Day	8% 13% 5% 10% 10% 6% 7% 7% 7% 8% 20%	1584
February	1st to 10th	Day	9% 13% 5% 11% 10% 5% 8% 5% 6% 5% 24%	1454
	11th to 20th	Day	8% 11% 5% 11% 9% 5% 5% 5% 6% 6% 28%	1575
	21st to end	Day	7% 12% 6% 8% 9% 5% 7% 6% 7% 9% 24%	1466
March	1st to 10th	Day	7% 10% 4 9% 9% 5% 8% 7% 7% 10% 25%	1800
	11th to 20th	Day	8% 10% 4 8% 8% 5% 7% 6% 7% 7% 30%	1864
	21st to end	Day	8% 11% 5% 8% 8% 5% 6% 7% 7% 9% 25%	2360
April	1st to 10th	Day	9% 13% 6% 7% 8% 5% 7% 5% 6% 8% 27%	2160
	11th to 20th	Day	9% 10% 5% 8% 8% 4 6% 6% 7% 7% 30%	2167
	21st to end	Day	9% 10% 4 8% 7% 4 6% 6% 7% 9% 31%	2461
May	1st to 10th	Day	10% 8% 4 7% 6% 4 6% 6% 6% 7% 35%	2520
	11th to 20th	Day	9% 6% 3 7% 6% 4 5% 6% 6% 8% 39%	2477
	21st to end	Day	13% 8% 3 7% 6% 4 5% 5% 7% 7% 34%	2799
June	1st to 10th	Day	15% 7% 3 7% 8% 4 5% 6% 6% 7% 32%	2736
	11th to 20th	Day	16% 7% 3 7% 7% 5% 7% 7% 6% 7% 28%	2880
	21st to end	Day	9% 5% 3 5% 6% 4 6% 6% 7% 8% 42%	2880
July	1st to 10th	Day	6% 4 2 4 5% 4 5% 5% 7% 8% 50%	2814
	11th to 20th	Day	4 3 2 5% 5% 3 5% 5% 5% 9% 54%	2562
	21st to end	Day	3 2 1 2 4 2 4 4 5% 7% 65%	2741
August	1st to 10th	Day	4 3 2 4 4 3 4 5% 6% 8% 57%	2507
	11th to 20th	Day	4 3 1 3 4 3 5% 5% 5% 8% 59%	2475
	21st to end	Day	7% 4 2 5% 5% 4 5% 5% 7% 9% 47%	2422
September	1st to 10th	Day	7% 5% 2 5% 5% 3 4 4 5% 8% 52%	2160
	11th to 20th	Day	8% 5% 3 6% 6% 4 5% 5% 6% 8% 44%	2134
	21st to end	Day	10% 7% 3 6% 6% 4 6% 6% 6% 9% 38%	1976
October	1st to 10th	Day	9% 8% 3 7% 7% 4 6% 5% 5% 7% 38%	1800
	11th to 20th	Day	12% 8% 4 7% 6% 4 5% 5% 7% 8% 34%	1729
	21st to end	Day	14% 9% 4 8% 7% 4 4 5% 6% 7% 32%	1782
November	1st to 10th	Day	14% 12% 4 9% 8% 4 6% 6% 7% 6% 23%	1585
	11th to 20th	Day	9% 10% 5% 9% 9% 4 7% 7% 6% 6% 26%	1520
	21st to end	Day	10% 11% 6% 11% 10% 5% 9% 6% 6% 7% 18%	1348
December	1st to 10th	Day	8% 10% 6% 12% 12% 5% 7% 7% 6% 6% 20%	1330
	11th to 20th	Day	9% 14% 6% 13% 11% 6% 6% 7% 7% 7% 15%	1682
	21st to end	Day	10% 14% 4 12% 11% 6% 8% 6% 5% 7% 16%	2182
January	1st to 10th	Night	13% 17% 6% 10% 10% 5% 8% 5% 5% 7% 13%	2783
	11th to 20th	Night	9% 16% 7% 15% 12% 5% 7% 6% 5% 6% 13%	2548
	21st to end	Night	8% 15% 6% 12% 10% 5% 8% 5% 5% 7% 19%	2772
February	1st to 10th	Night	11% 15% 6% 10% 9% 5% 6% 6% 6% 6% 21%	2505
	11th to 20th	Night	9% 14% 5% 10% 8% 3 6% 5% 4 7% 29%	2272
	21st to end	Night	8% 14% 5% 9% 8% 4 5% 6% 5% 7% 28%	1790
March	1st to 10th	Night	8% 11% 6% 8% 8% 5% 6% 6% 6% 7% 30%	2160
	11th to 20th	Night	8% 10% 5% 8% 7% 4 5% 6% 6% 7% 34%	2092
	21st to end	Night	8% 9% 5% 9% 7% 5% 7% 6% 6% 8% 31%	1995
April	1st to 10th	Night	8% 8% 4 6% 6% 5% 5% 6% 6% 9% 37%	1800
	11th to 20th	Night	9% 8% 5% 8% 8% 5% 7% 6% 7% 6% 31%	1744
	21st to end	Night	9% 8% 4 6% 6% 4 6% 5% 6% 7% 38%	1496
May	1st to 10th	Night	8% 8% 3 8% 9% 4 6% 6% 5% 6% 37%	1440
	11th to 20th	Night	7% 6% 2 5% 6% 4 5% 6% 7% 10% 41%	1416
	21st to end	Night	13% 7% 3 6% 4 3 4 6% 6% 9% 38%	1472
June	1st to 10th	Night	12% 7% 4 5% 6% 4 5% 6% 6% 9% 36%	1220
	11th to 20th	Night	14% 5% 3 7% 7% 3 5% 6% 8% 8% 33%	1080
	21st to end	Night	5% 5% 2 7% 6% 2 6% 7% 7% 9% 44%	1080
July	1st to 10th	Night	5% 5% 2 4 4 3 5% 6% 6% 9% 51%	1142
	11th to 20th	Night	4 3 1 3 4 2 4 5% 5% 9% 59%	1394
	21st to end	Night	4 2 1 2 3 2 4 3 5% 7% 68%	1576
August	1st to 10th	Night	4 2 1 2 3 3 3 5% 6% 8% 62%	1432
	11th to 20th	Night	4 2 1 3 3 2 4 4 5% 8% 65%	1424
	21st to end	Night	5% 2 2 5% 4 3 5% 5% 6% 8% 54%	1932
September	1st to 10th	Night	5% 3 2 4 5% 3 5% 4 6% 7% 55%	1800
	11th to 20th	Night	8% 5% 3 3 5% 3 3 5% 5% 7% 52%	1826
	21st to end	Night	10% 6% 3 6% 5% 3 5% 4 4 8% 45%	1982
October	1st to 10th	Night	9% 7% 3 6% 6% 3 5% 5% 6% 7% 44%	2160
	11th to 20th	Night	12% 8% 3 6% 7% 4 5% 5% 5% 7% 38%	2230
	21st to end	Night	12% 9% 3 7% 8% 4 5% 5% 6% 7% 35%	2574
November	1st to 10th	Night	16% 13% 5% 9% 7% 4 6% 5% 6% 7% 24%	2490
	11th to 20th	Night	12% 12% 4 9% 9% 6% 7% 6% 5% 6% 25%	2660
	21st to end	Night	11% 13% 7% 11% 8% 4 6% 7% 7% 7% 20%	2812
December	1st to 10th	Night	10% 14% 6% 11% 9% 4 6% 6% 7% 6% 22%	2850
	11th to 20th	Night	10% 17% 7% 15% 11% 6% 7% 6% 4 5% 11%	3510
	21st to end	Night	10% 14% 6% 13% 12% 6% 7% 6% 5% 5% 15%	5452

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	66% 17% 12% 4 1	1389
	11th to 20th	Day	59% 17% 14% 7% 1 1	1451
	21st to end	Day	59% 15% 16% 8% 1 1	1584
February	1st to 10th	Day	61% 12% 13% 9% 4 1	1454
	11th to 20th	Day	55% 14% 16% 12% 3	1584
	21st to end	Day	55% 15% 16% 11% 3	1466
March	1st to 10th	Day	54% 15% 14% 12% 4 1	1800
	11th to 20th	Day	51% 13% 15% 15% 5%	1864
	21st to end	Day	55% 12% 19% 11% 4	2360
April	1st to 10th	Day	54% 13% 15% 14% 3	2160
	11th to 20th	Day	52% 10% 14% 16% 6% 1	2167
	21st to end	Day	50% 11% 16% 16% 7%	2461
May	1st to 10th	Day	46% 11% 17% 17% 9% 1	2520
	11th to 20th	Day	42% 12% 17% 21% 8%	2480
	21st to end	Day	48% 12% 16% 18% 6% 1	2800
June	1st to 10th	Day	50% 12% 13% 14% 9% 3	2736
	11th to 20th	Day	54% 12% 12% 15% 6% 1	2880
	21st to end	Day	38% 12% 17% 19% 12% 2	2880
July	1st to 10th	Day	31% 11% 14% 22% 17% 5%	2738
	11th to 20th	Day	27% 9% 15% 27% 18% 4	2484
	21st to end	Day	17% 6% 16% 28% 28% 5%	2589
August	1st to 10th	Day	23% 10% 17% 26% 20% 4	2490
	11th to 20th	Day	24% 8% 17% 29% 19% 3	2475
	21st to end	Day	32% 11% 17% 27% 11% 1	2422
September	1st to 10th	Day	29% 10% 16% 30% 12% 3	2160
	11th to 20th	Day	35% 12% 14% 23% 14% 1	2134
	21st to end	Day	42% 11% 20% 18% 8% 1	1976
October	1st to 10th	Day	43% 10% 20% 22% 5%	1800
	11th to 20th	Day	46% 11% 21% 19% 3	1729
	21st to end	Day	50% 12% 19% 15% 4	1782
November	1st to 10th	Day	60% 13% 13% 11% 3	1585
	11th to 20th	Day	58% 14% 15% 8% 3 1	1520
	21st to end	Day	60% 15% 17% 7% 1	1348
December	1st to 10th	Day	61% 14% 12% 12% 1	1330
	11th to 20th	Day	63% 17% 13% 6% 2	1684
	21st to end	Day	59% 15% 16% 9% 1	2182
January	1st to 10th	Night	67% 12% 12% 7% 2	2783
	11th to 20th	Night	69% 12% 13% 5% 1	2548
	21st to end	Night	61% 14% 14% 8% 3	2772
February	1st to 10th	Night	60% 12% 13% 10% 4 1	2505
	11th to 20th	Night	55% 10% 15% 16% 4	2274
	21st to end	Night	55% 10% 16% 12% 6%	1790
March	1st to 10th	Night	52% 11% 17% 12% 7%	2160
	11th to 20th	Night	48% 11% 16% 18% 6% 1	2093
	21st to end	Night	50% 12% 17% 17% 4	1995
April	1st to 10th	Night	41% 16% 21% 16% 6%	1800
	11th to 20th	Night	51% 11% 14% 16% 7% 1	1744
	21st to end	Night	45% 11% 14% 21% 9%	1496
May	1st to 10th	Night	45% 12% 15% 16% 10% 1	1440
	11th to 20th	Night	37% 11% 19% 25% 9% 1	1416
	21st to end	Night	44% 9% 17% 21% 9%	1472
June	1st to 10th	Night	44% 12% 13% 19% 8% 4	1220
	11th to 20th	Night	46% 11% 14% 20% 9%	1080
	21st to end	Night	33% 14% 19% 20% 11% 2	1080
July	1st to 10th	Night	28% 9% 14% 24% 17% 7%	1109
	11th to 20th	Night	23% 8% 18% 28% 20% 3	1349
	21st to end	Night	15% 6% 14% 28% 30% 7%	1488
August	1st to 10th	Night	20% 7% 16% 27% 26% 6%	1424
	11th to 20th	Night	19% 6% 16% 32% 25% 3	1424
	21st to end	Night	26% 10% 17% 30% 16% 2	1932
September	1st to 10th	Night	27% 11% 16% 28% 16% 4	1800
	11th to 20th	Night	30% 11% 15% 23% 19% 3	1826
	21st to end	Night	38% 10% 18% 23% 10% 2	1982
October	1st to 10th	Night	38% 11% 18% 24% 8%	2160
	11th to 20th	Night	46% 11% 16% 21% 7%	2230
	21st to end	Night	48% 10% 18% 19% 4	2574
November	1st to 10th	Night	58% 13% 13% 12% 4	2490
	11th to 20th	Night	58% 15% 12% 10% 5%	2660
	21st to end	Night	60% 14% 15% 8% 3	2812
December	1st to 10th	Night	58% 12% 16% 11% 3	2850
	11th to 20th	Night	68% 15% 10% 5% 1	3507
	21st to end	Night	61% 15% 16% 7% 1	5452

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	16% 13% 27% 23% 13% 8%	180
	11th to 20th	Day	16% 9% 28% 23% 19% 4	163
	21st to end	Day	18% 7% 30% 30% 13% 3	176
February	1st to 10th	Day	17% 21% 35% 21% 5% 1	174
	11th to 20th	Day	14% 19% 31% 28% 7% 1	335
	21st to end	Day	11% 15% 29% 30% 12% 2	340
March	1st to 10th	Day	14% 23% 29% 22% 10% 2	420
	11th to 20th	Day	14% 20% 25% 24% 13% 3	420
	21st to end	Day	18% 21% 26% 18% 15% 2	462
April	1st to 10th	Day	20% 21% 27% 20% 11% 1	420
	11th to 20th	Day	19% 20% 25% 19% 12% 4	412
	21st to end	Day	13% 20% 31% 21% 10% 5%	420
May	1st to 10th	Day	11% 18% 31% 27% 11% 3	423
	11th to 20th	Day	13% 12% 24% 28% 20% 5%	448
	21st to end	Day	16% 11% 20% 28% 19% 5%	561
June	1st to 10th	Day	18% 12% 26% 29% 14% 2	666
	11th to 20th	Day	16% 13% 28% 28% 13% 2	810
	21st to end	Day	10% 11% 25% 29% 21% 4	810
July	1st to 10th	Day	9% 9% 21% 35% 23% 2	733
	11th to 20th	Day	5% 11% 27% 32% 21% 4	483
	21st to end	Day	5% 7% 24% 35% 24% 7%	487
August	1st to 10th	Day	4 8% 21% 35% 23% 9%	447
	11th to 20th	Day	6% 7% 25% 34% 20% 8%	437
	21st to end	Day	10% 9% 25% 29% 19% 7%	495
September	1st to 10th	Day	10% 12% 24% 32% 17% 4	450
	11th to 20th	Day	11% 12% 25% 28% 20% 4	450
	21st to end	Day	18% 13% 26% 26% 14% 3	450
October	1st to 10th	Day	16% 12% 25% 25% 18% 5%	450
	11th to 20th	Day	16% 16% 26% 23% 16% 3	379
	21st to end	Day	23% 11% 28% 25% 12% 2	297
November	1st to 10th	Day	19% 12% 29% 25% 12% 2	228
	11th to 20th	Day	16% 17% 28% 22% 13% 4	180
	21st to end	Day	16% 12% 29% 23% 14% 6%	180
December	1st to 10th	Day	17% 9% 20% 24% 23% 7%	180
	11th to 20th	Day	17% 9% 32% 23% 13% 5%	180
	21st to end	Day	17% 7% 26% 35% 10% 5%	198
January	1st to 10th	Night	23% 12% 26% 26% 11% 2	837
	11th to 20th	Night	18% 9% 26% 30% 15% 2	728
	21st to end	Night	16% 8% 27% 30% 16% 3	792
February	1st to 10th	Night	20% 11% 25% 30% 12% 2	720
	11th to 20th	Night	17% 10% 25% 35% 13% 1	704
	21st to end	Night	15% 8% 25% 30% 18% 4	592
March	1st to 10th	Night	15% 12% 25% 29% 17% 2	720
	11th to 20th	Night	14% 12% 27% 32% 15% 1	720
	21st to end	Night	13% 10% 26% 30% 17% 3	792
April	1st to 10th	Night	12% 11% 24% 31% 20% 2	720
	11th to 20th	Night	15% 10% 26% 31% 18% 1	676
	21st to end	Night	13% 9% 29% 32% 15% 2	416
May	1st to 10th	Night	13% 8% 19% 37% 21% 1	360
	11th to 20th	Night	12% 4 19% 38% 24% 2	354
	21st to end	Night	15% 6% 18% 31% 26% 4	389
June	1st to 10th	Night	16% 5% 28% 33% 16% 1	360
	11th to 20th	Night	15% 7% 25% 32% 19% 3	360
	21st to end	Night	8% 6% 20% 39% 24% 3	360
July	1st to 10th	Night	9% 5% 15% 35% 34% 2	350
	11th to 20th	Night	5% 7% 20% 34% 33% 2	348
	21st to end	Night	6% 1 14% 40% 36% 4	394
August	1st to 10th	Night	5% 1 13% 35% 37% 8%	358
	11th to 20th	Night	4 2 12% 40% 35% 6%	356
	21st to end	Night	6% 4 17% 38% 32% 3	744
September	1st to 10th	Night	7% 5% 18% 37% 27% 5%	720
	11th to 20th	Night	11% 5% 16% 28% 33% 7%	720
	21st to end	Night	15% 8% 18% 35% 21% 4	720
October	1st to 10th	Night	13% 5% 18% 36% 24% 3	720
	11th to 20th	Night	17% 9% 19% 30% 22% 3	720
	21st to end	Night	18% 9% 26% 31% 13% 3	792
November	1st to 10th	Night	23% 10% 21% 35% 9% 1	740
	11th to 20th	Night	20% 14% 26% 25% 13% 2	760
	21st to end	Night	18% 11% 25% 30% 13% 3	912
December	1st to 10th	Night	14% 9% 28% 32% 14% 2	950
	11th to 20th	Night	18% 10% 29% 32% 11% 1	950
	21st to end	Night	21% 9% 28% 32% 9% 1	1114

Page generated at 2024-01-09 13:24:22. Version ac07

Copyright 2024 Attilla Danko