Kirkland
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kirkland clear sky chart from 2005-11-06 to 2024-01-16.

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	13% 9% 4 7% 6% 3 5% 5% 5% 7% 36%	74822
	Night	14% 9% 4 6% 5% 3 4 4 5% 7% 39%	75014
Transparency	Day	46% 7% 12% 22% 12% 1	74523
	Night	45% 6% 11% 22% 14% 2	74834
Seeing	Day	16% 10% 29% 26% 14% 6%	14671
	Night	17% 9% 31% 30% 12% 1	24659

By Month

Percentage Cloud Cover SE (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	13% 11% 5% 9% 8% 3 6% 5% 5% 8% 26%	1517
	11th to 20th	Day	13% 15% 7% 12% 8% 3 4 5% 6% 6% 23%	1485
	21st to end	Day	14% 17% 7% 10% 6% 3 4 4 5% 6% 24%	1664
February	1st to 10th	Day	14% 13% 5% 9% 7% 4 8% 5% 5% 6% 25%	1620
	11th to 20th	Day	14% 11% 3 7% 7% 4 5% 5% 5% 5% 35%	1736
	21st to end	Day	14% 13% 6% 10% 6% 3 4 4 5% 6% 30%	1480
March	1st to 10th	Day	14% 12% 5% 8% 6% 3 3 5% 4 6% 33%	1800
	11th to 20th	Day	14% 8% 3 7% 5% 4 5% 4 4 8% 36%	1879
	21st to end	Day	20% 11% 4 9% 7% 4 5% 5% 6% 6% 25%	2366
April	1st to 10th	Day	18% 10% 5% 7% 6% 4 5% 4 4 6% 31%	2160
	11th to 20th	Day	17% 9% 3 5% 6% 4 6% 5% 6% 7% 33%	2134
	21st to end	Day	19% 8% 3 7% 6% 4 5% 5% 5% 6% 32%	2222
May	1st to 10th	Day	17% 8% 3 6% 7% 3 6% 6% 6% 8% 30%	2342
	11th to 20th	Day	18% 8% 4 6% 6% 3 5% 5% 6% 7% 34%	2479
	21st to end	Day	13% 7% 3 6% 6% 3 6% 6% 5% 8% 36%	2725
June	1st to 10th	Day	9% 5% 2 5% 5% 4 5% 5% 7% 8% 45%	2520
	11th to 20th	Day	10% 5% 2 4 4 2 5% 5% 6% 10% 45%	2520
	21st to end	Day	11% 6% 3 6% 5% 4 5% 6% 7% 10% 38%	2520
July	1st to 10th	Day	7% 5% 2 4 5% 3 5% 6% 7% 10% 46%	2520
	11th to 20th	Day	8% 5% 2 4 4 3 5% 6% 7% 10% 46%	2520
	21st to end	Day	6% 5% 2 6% 6% 3 5% 6% 7% 10% 44%	2743
August	1st to 10th	Day	8% 5% 2 6% 5% 4 4 6% 7% 10% 43%	2476
	11th to 20th	Day	10% 4 2 5% 5% 3 5% 5% 7% 9% 45%	2125
	21st to end	Day	10% 4 2 4 5% 3 4 5% 6% 8% 48%	2376
September	1st to 10th	Day	12% 5% 2 4 5% 3 5% 5% 6% 8% 45%	2160
	11th to 20th	Day	13% 4 2 4 3 3 3 4 5% 7% 52%	2078
	21st to end	Day	11% 6% 3 6% 5% 3 4 4 6% 7% 44%	1980
October	1st to 10th	Day	13% 6% 3 5% 4 3 4 4 5% 6% 46%	1882
	11th to 20th	Day	20% 9% 3 6% 5% 3 4 5% 5% 6% 34%	1800
	21st to end	Day	21% 9% 3 6% 5% 2 3 4 4 5% 37%	1803
November	1st to 10th	Day	12% 7% 3 6% 5% 2 4 5% 5% 6% 45%	1672
	11th to 20th	Day	15% 11% 5% 8% 6% 4 4 5% 4 7% 31%	1710
	21st to end	Day	17% 11% 4 9% 5% 3 3 3 4 5% 36%	1587
December	1st to 10th	Day	15% 12% 5% 9% 6% 4 4 4 4 6% 31%	1520
	11th to 20th	Day	12% 14% 6% 8% 7% 4 5% 5% 5% 6% 28%	1918
	21st to end	Day	20% 22% 9% 12% 7% 3 4 3 2 4 15%	2783
January	1st to 10th	Night	14% 12% 5% 9% 7% 3 4 4 4 5% 34%	2648
	11th to 20th	Night	15% 15% 7% 10% 6% 3 4 4 5% 5% 27%	2603
	21st to end	Night	14% 12% 7% 10% 7% 4 4 4 6% 7% 25%	2690
February	1st to 10th	Night	15% 14% 7% 7% 6% 4 4 3 4 6% 31%	2340
	11th to 20th	Night	14% 9% 4 8% 6% 3 5% 4 5% 6% 37%	2108
	21st to end	Night	18% 12% 5% 7% 5% 2 4 3 4 7% 34%	1776
March	1st to 10th	Night	17% 10% 4 6% 5% 3 5% 4 5% 6% 36%	2160
	11th to 20th	Night	12% 7% 4 5% 5% 3 5% 5% 6% 7% 41%	2098
	21st to end	Night	20% 10% 5% 7% 5% 3 4 4 4 6% 31%	1990
April	1st to 10th	Night	17% 9% 4 5% 4 3 5% 5% 4 5% 39%	1800
	11th to 20th	Night	18% 9% 3 6% 5% 3 4 4 4 6% 39%	1775
	21st to end	Night	18% 8% 3 6% 4 3 3 5% 5% 7% 38%	1735
May	1st to 10th	Night	16% 6% 3 6% 5% 3 6% 5% 7% 7% 37%	1615
	11th to 20th	Night	16% 7% 3 5% 5% 3 4 5% 6% 9% 38%	1416
	21st to end	Night	11% 7% 3 5% 6% 3 6% 5% 7% 9% 39%	1551
June	1st to 10th	Night	9% 4 2 4 6% 4 5% 5% 7% 7% 48%	1440
	11th to 20th	Night	9% 5% 3 5% 4 3 4 5% 6% 8% 47%	1440
	21st to end	Night	8% 5% 3 5% 4 5% 6% 4 8% 8% 44%	1440
July	1st to 10th	Night	7% 4 1 3 5% 2 4 5% 7% 12% 50%	1440
	11th to 20th	Night	7% 4 2 4 4 3 4 5% 5% 9% 53%	1440
	21st to end	Night	6% 4 2 4 5% 3 4 5% 6% 10% 49%	1575
August	1st to 10th	Night	4 3 2 5% 5% 3 5% 5% 8% 10% 50%	1459
	11th to 20th	Night	8% 3 2 4 4 2 5% 4 5% 9% 53%	1776
	21st to end	Night	8% 4 2 4 4 2 3 5% 6% 9% 53%	1980
September	1st to 10th	Night	10% 6% 2 4 4 2 3 4 4 6% 54%	1800
	11th to 20th	Night	10% 4 1 4 4 3 4 4 5% 6% 54%	1863
	21st to end	Night	11% 6% 2 5% 4 4 4 4 5% 7% 49%	1980
October	1st to 10th	Night	12% 6% 3 5% 5% 2 4 4 4 5% 50%	2075
	11th to 20th	Night	17% 8% 3 5% 4 2 4 3 4 6% 44%	2160
	21st to end	Night	20% 10% 3 6% 4 2 4 4 5% 5% 38%	2551
November	1st to 10th	Night	11% 8% 3 5% 4 3 4 4 4 6% 49%	2406
	11th to 20th	Night	15% 10% 4 7% 5% 3 4 4 5% 7% 36%	2470
	21st to end	Night	17% 10% 5% 6% 5% 2 4 4 5% 6% 38%	2591
December	1st to 10th	Night	16% 10% 4 8% 6% 4 5% 4 5% 7% 31%	2660
	11th to 20th	Night	15% 13% 5% 9% 5% 3 5% 4 5% 6% 31%	3279
	21st to end	Night	21% 16% 7% 10% 6% 4 4 5% 5% 5% 17%	4884

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	56% 5% 11% 16% 10%	1518
	11th to 20th	Day	62% 5% 13% 14% 6%	1485
	21st to end	Day	61% 6% 11% 13% 9% 1	1664
February	1st to 10th	Day	59% 6% 12% 14% 8% 1	1620
	11th to 20th	Day	50% 7% 11% 21% 9% 2	1746
	21st to end	Day	55% 6% 9% 19% 10% 1	1480
March	1st to 10th	Day	52% 5% 14% 21% 7% 1	1800
	11th to 20th	Day	46% 7% 13% 22% 11% 1	1879
	21st to end	Day	59% 7% 10% 17% 6% 1	2366
April	1st to 10th	Day	54% 7% 10% 21% 9%	2160
	11th to 20th	Day	49% 7% 10% 20% 11% 2	2134
	21st to end	Day	52% 6% 12% 17% 12% 1	2222
May	1st to 10th	Day	51% 8% 12% 22% 7%	2342
	11th to 20th	Day	49% 7% 12% 22% 10%	2483
	21st to end	Day	45% 9% 12% 19% 14% 2	2725
June	1st to 10th	Day	34% 8% 14% 27% 16% 2	2520
	11th to 20th	Day	33% 7% 13% 25% 19% 2	2520
	21st to end	Day	40% 9% 13% 23% 13% 2	2520
July	1st to 10th	Day	32% 8% 14% 29% 13% 3	2451
	11th to 20th	Day	31% 8% 16% 27% 16% 2	2445
	21st to end	Day	32% 9% 18% 25% 14% 3	2591
August	1st to 10th	Day	33% 9% 17% 29% 11% 2	2461
	11th to 20th	Day	33% 8% 16% 27% 15% 1	2125
	21st to end	Day	31% 8% 11% 27% 20% 3	2376
September	1st to 10th	Day	36% 7% 12% 25% 17% 3	2160
	11th to 20th	Day	30% 6% 12% 30% 19% 3	2078
	21st to end	Day	37% 6% 11% 27% 18% 1	1980
October	1st to 10th	Day	38% 6% 11% 26% 17% 1	1882
	11th to 20th	Day	49% 6% 11% 20% 13% 1	1800
	21st to end	Day	50% 5% 11% 22% 11% 2	1803
November	1st to 10th	Day	40% 4 14% 24% 16% 2	1672
	11th to 20th	Day	53% 4 12% 21% 9% 1	1710
	21st to end	Day	52% 4 12% 22% 9%	1587
December	1st to 10th	Day	54% 6% 12% 18% 8% 1	1520
	11th to 20th	Day	55% 5% 13% 17% 7% 2	1915
	21st to end	Day	76% 4 7% 9% 4	2783
January	1st to 10th	Night	53% 5% 11% 19% 12% 1	2648
	11th to 20th	Night	59% 6% 12% 13% 9%	2603
	21st to end	Night	58% 6% 11% 14% 9% 1	2690
February	1st to 10th	Night	56% 4 10% 17% 12% 1	2340
	11th to 20th	Night	48% 5% 12% 21% 13% 1	2109
	21st to end	Night	51% 4 11% 19% 11% 4	1776
March	1st to 10th	Night	49% 6% 13% 21% 10% 1	2160
	11th to 20th	Night	41% 6% 13% 20% 17% 3	2098
	21st to end	Night	55% 5% 10% 19% 10% 1	1990
April	1st to 10th	Night	46% 6% 11% 21% 13% 2	1800
	11th to 20th	Night	47% 6% 6% 22% 16% 4	1775
	21st to end	Night	45% 7% 12% 23% 11% 3	1735
May	1st to 10th	Night	44% 8% 14% 23% 11%	1615
	11th to 20th	Night	42% 8% 13% 22% 14% 2	1417
	21st to end	Night	39% 9% 12% 21% 17% 2	1552
June	1st to 10th	Night	32% 6% 14% 25% 19% 3	1440
	11th to 20th	Night	34% 7% 11% 24% 23% 3	1440
	21st to end	Night	37% 8% 14% 22% 18% 2	1440
July	1st to 10th	Night	28% 8% 14% 28% 17% 4	1400
	11th to 20th	Night	27% 6% 15% 29% 20% 2	1392
	21st to end	Night	28% 7% 16% 25% 18% 5%	1487
August	1st to 10th	Night	26% 10% 17% 31% 14% 3	1450
	11th to 20th	Night	27% 9% 14% 30% 20% 1	1776
	21st to end	Night	27% 7% 12% 28% 22% 4	1980
September	1st to 10th	Night	31% 6% 10% 26% 23% 3	1800
	11th to 20th	Night	30% 6% 8% 32% 21% 2	1863
	21st to end	Night	34% 6% 11% 30% 17% 2	1980
October	1st to 10th	Night	35% 6% 9% 27% 21% 2	2075
	11th to 20th	Night	42% 4 11% 23% 19% 2	2160
	21st to end	Night	48% 5% 10% 24% 12% 1	2551
November	1st to 10th	Night	37% 5% 9% 27% 19% 3	2406
	11th to 20th	Night	48% 5% 12% 21% 13% 1	2470
	21st to end	Night	48% 5% 12% 23% 12% 1	2591
December	1st to 10th	Night	53% 6% 12% 20% 8% 1	2660
	11th to 20th	Night	54% 5% 12% 19% 9% 1	3281
	21st to end	Night	68% 6% 9% 12% 5%	4884

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	20% 11% 36% 25% 7%	270
	11th to 20th	Day	24% 11% 39% 21% 4 2	257
	21st to end	Day	23% 11% 37% 24% 4 1	264
February	1st to 10th	Day	20% 18% 39% 19% 4	240
	11th to 20th	Day	25% 16% 32% 23% 5%	240
	21st to end	Day	25% 21% 37% 16% 1 1	198
March	1st to 10th	Day	18% 20% 39% 19% 4	240
	11th to 20th	Day	23% 15% 36% 15% 10% 1	240
	21st to end	Day	28% 13% 31% 19% 7% 2	452
April	1st to 10th	Day	24% 12% 35% 24% 5%	420
	11th to 20th	Day	22% 19% 27% 19% 10% 3	412
	21st to end	Day	24% 12% 30% 23% 10% 2	420
May	1st to 10th	Day	20% 14% 30% 24% 9% 3	425
	11th to 20th	Day	22% 10% 29% 26% 12% 2	625
	21st to end	Day	16% 8% 28% 25% 16% 7%	679
June	1st to 10th	Day	8% 7% 31% 29% 19% 6%	630
	11th to 20th	Day	11% 6% 31% 31% 16% 6%	630
	21st to end	Day	11% 7% 29% 32% 15% 5%	630
July	1st to 10th	Day	8% 3 18% 28% 26% 16%	621
	11th to 20th	Day	9% 5% 23% 33% 20% 10%	618
	21st to end	Day	7% 3 22% 38% 23% 8%	684
August	1st to 10th	Day	9% 3 19% 32% 26% 12%	626
	11th to 20th	Day	10% 5% 15% 27% 24% 18%	439
	21st to end	Day	9% 4 17% 32% 25% 13%	495
September	1st to 10th	Day	14% 7% 20% 30% 24% 7%	450
	11th to 20th	Day	9% 4 21% 29% 24% 13%	450
	21st to end	Day	13% 12% 25% 24% 19% 7%	450
October	1st to 10th	Day	15% 9% 29% 26% 17% 4	352
	11th to 20th	Day	23% 21% 30% 20% 6%	270
	21st to end	Day	32% 13% 29% 21% 5% 1	297
November	1st to 10th	Day	14% 15% 36% 22% 10% 3	270
	11th to 20th	Day	21% 17% 37% 17% 7% 1	270
	21st to end	Day	23% 10% 39% 21% 7%	270
December	1st to 10th	Day	18% 15% 40% 19% 6% 1	270
	11th to 20th	Day	17% 10% 41% 21% 10%	270
	21st to end	Day	25% 18% 40% 14% 2	297
January	1st to 10th	Night	19% 14% 38% 24% 5%	950
	11th to 20th	Night	21% 13% 38% 22% 5% 1	930
	21st to end	Night	20% 10% 36% 29% 5%	990
February	1st to 10th	Night	25% 9% 39% 22% 4	900
	11th to 20th	Night	20% 12% 37% 26% 5%	713
	21st to end	Night	23% 12% 39% 21% 4	592
March	1st to 10th	Night	21% 11% 37% 25% 6%	720
	11th to 20th	Night	16% 10% 37% 31% 7%	658
	21st to end	Night	23% 11% 33% 25% 7% 1	594
April	1st to 10th	Night	21% 13% 36% 25% 5%	540
	11th to 20th	Night	23% 12% 30% 28% 6%	533
	21st to end	Night	20% 9% 35% 28% 8%	540
May	1st to 10th	Night	18% 7% 35% 31% 8% 1	540
	11th to 20th	Night	18% 7% 32% 31% 12%	531
	21st to end	Night	15% 4 28% 34% 19%	584
June	1st to 10th	Night	9% 4 28% 42% 16%	540
	11th to 20th	Night	11% 4 29% 44% 11% 1	540
	21st to end	Night	9% 4 28% 39% 20% 1	540
July	1st to 10th	Night	8% 2 16% 38% 33% 4	525
	11th to 20th	Night	9% 2 22% 40% 24% 3	522
	21st to end	Night	6% 1 20% 47% 25% 1	591
August	1st to 10th	Night	6% 2 13% 47% 28% 4	537
	11th to 20th	Night	7% 3 14% 40% 31% 5%	534
	21st to end	Night	9% 2 17% 40% 30% 3	594
September	1st to 10th	Night	11% 3 21% 35% 25% 4	540
	11th to 20th	Night	11% 5% 20% 34% 28% 3	603
	21st to end	Night	13% 8% 25% 32% 20% 3	720
October	1st to 10th	Night	14% 6% 28% 33% 18% 1	720
	11th to 20th	Night	21% 12% 32% 27% 9%	720
	21st to end	Night	25% 12% 32% 23% 8%	792
November	1st to 10th	Night	16% 10% 39% 24% 10% 1	740
	11th to 20th	Night	20% 14% 35% 24% 7%	760
	21st to end	Night	20% 12% 38% 24% 6%	881
December	1st to 10th	Night	21% 13% 38% 24% 5%	950
	11th to 20th	Night	22% 11% 35% 26% 4 1	950
	21st to end	Night	27% 14% 34% 21% 3	1045

Page generated at 2024-01-13 18:28:33. Version ac07

Copyright 2024 Attilla Danko