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 2024-12-09.

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% 3 8% 5% 4 5% 4 6% 7% 37%	101691
	Night	14% 10% 4 8% 4 4 4 4 5% 6% 38%	98183
Transparency	Day	44% 7% 12% 23% 13% 2	105243
	Night	44% 6% 11% 22% 15% 2	102772
Seeing	Day	16% 10% 29% 26% 14% 5%	15944
	Night	17% 9% 31% 30% 12% 1	25827

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	11% 13% 9% 15% 6% 5% 4 3 4 5% 25%	2527
	11th to 20th	Day	12% 13% 5% 15% 6% 5% 4 8% 9% 5% 19%	2530
	21st to end	Day	16% 19% 9% 11% 6% 3 4 3 4 5% 19%	2919
February	1st to 10th	Day	13% 14% 4 10% 6% 6% 7% 4 4 6% 26%	1710
	11th to 20th	Day	13% 11% 3 8% 6% 5% 4 4 6% 5% 36%	1835
	21st to end	Day	13% 13% 5% 10% 5% 4 4 4 5% 6% 31%	1570
March	1st to 10th	Day	13% 13% 4 7% 4 4 4 3 4 6% 39%	3120
	11th to 20th	Day	11% 6% 3 8% 5% 5% 5% 4 6% 7% 40%	3309
	21st to end	Day	19% 13% 4 13% 6% 5% 5% 3 5% 5% 20%	4155
April	1st to 10th	Day	18% 12% 3 8% 6% 4 4 4 4 6% 31%	2280
	11th to 20th	Day	17% 9% 2 6% 5% 6% 5% 4 6% 6% 34%	2254
	21st to end	Day	19% 8% 3 8% 5% 5% 5% 4 5% 5% 33%	2346
May	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 5% 6% 7% 35%	4098
	11th to 20th	Day	14% 7% 3 6% 4 4 4 3 5% 7% 42%	4399
	21st to end	Day	11% 7% 2 6% 4 5% 5% 4 6% 10% 40%	4824
June	1st to 10th	Day	9% 5% 2 6% 4 5% 4 4 7% 8% 45%	2660
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 4 7% 10% 45%	2660
	21st to end	Day	11% 7% 2 7% 4 5% 5% 5% 7% 9% 38%	2660
July	1st to 10th	Day	10% 8% 3 7% 6% 5% 6% 5% 7% 9% 33%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 5% 5% 7% 10% 48%	4440
	21st to end	Day	8% 6% 3 8% 5% 5% 5% 4 7% 9% 40%	4813
August	1st to 10th	Day	10% 6% 2 6% 4 4 5% 4 7% 9% 43%	4364
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 4 7% 10% 44%	3729
	21st to end	Day	8% 5% 2 5% 4 5% 5% 4 6% 9% 47%	4180
September	1st to 10th	Day	12% 5% 2 5% 4 4 5% 3 5% 8% 47%	2280
	11th to 20th	Day	12% 4 2 4 3 4 3 3 5% 8% 52%	2193
	21st to end	Day	12% 6% 2 7% 5% 3 4 3 6% 7% 45%	2090
October	1st to 10th	Day	13% 6% 2 6% 3 4 4 3 5% 6% 47%	1986
	11th to 20th	Day	18% 9% 3 7% 4 3 4 4 5% 6% 36%	1900
	21st to end	Day	20% 9% 3 8% 4 3 3 3 5% 5% 37%	1903
November	1st to 10th	Day	12% 9% 2 7% 4 4 4 3 4 6% 44%	1762
	11th to 20th	Day	15% 12% 4 9% 6% 4 4 5% 5% 7% 30%	1800
	21st to end	Day	17% 12% 4 10% 4 3 3 2 4 5% 35%	1670
December	1st to 10th	Day	14% 13% 5% 9% 6% 4 4 3 4 6% 32%	1584
	11th to 20th	Day	12% 15% 5% 9% 7% 5% 5% 4 5% 6% 28%	1918
	21st to end	Day	20% 22% 9% 13% 5% 3 4 2 2 4 15%	2783
January	1st to 10th	Night	13% 14% 6% 13% 5% 4 3 3 4 4 29%	4428
	11th to 20th	Night	14% 18% 7% 13% 6% 4 3 6% 7% 4 19%	4440
	21st to end	Night	19% 19% 8% 10% 6% 5% 3 2 4 5% 20%	4746
February	1st to 10th	Night	14% 15% 5% 8% 5% 5% 4 3 4 6% 32%	2470
	11th to 20th	Night	13% 9% 4 8% 4 4 4 3 5% 6% 38%	2229
	21st to end	Night	17% 13% 5% 8% 4 3 3 3 4 7% 34%	1884
March	1st to 10th	Night	18% 10% 3 6% 3 4 4 2 4 5% 42%	3733
	11th to 20th	Night	9% 7% 2 6% 5% 4 5% 3 5% 6% 47%	3682
	21st to end	Night	22% 12% 5% 11% 5% 3 4 3 4 4 27%	3476
April	1st to 10th	Night	17% 10% 3 5% 4 4 4 4 4 5% 39%	1900
	11th to 20th	Night	18% 10% 2 6% 5% 4 4 3 4 6% 39%	1875
	21st to end	Night	17% 9% 3 7% 4 4 4 4 5% 6% 38%	1831
May	1st to 10th	Night	16% 7% 3 6% 5% 5% 5% 4 6% 7% 36%	2795
	11th to 20th	Night	13% 6% 2 5% 4 5% 5% 4 7% 8% 40%	2506
	21st to end	Night	9% 8% 2 6% 4 4 5% 4 7% 8% 43%	2743
June	1st to 10th	Night	9% 4 1 5% 5% 4 5% 4 7% 8% 47%	1520
	11th to 20th	Night	8% 6% 2 6% 3 4 4 4 7% 8% 47%	1520
	21st to end	Night	9% 7% 2 6% 4 6% 5% 4 8% 7% 44%	1520
July	1st to 10th	Night	14% 7% 2 7% 5% 4 4 4 6% 8% 38%	2530
	11th to 20th	Night	5% 4 2 5% 4 4 4 4 6% 8% 53%	2530
	21st to end	Night	6% 5% 2 7% 5% 5% 6% 5% 7% 9% 43%	2750
August	1st to 10th	Night	5% 4 2 6% 4 5% 4 4 6% 9% 50%	2572
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 6% 8% 48%	3100
	21st to end	Night	9% 4 1 5% 4 4 4 3 6% 9% 51%	3476
September	1st to 10th	Night	9% 6% 2 5% 4 3 3 3 4 6% 55%	1900
	11th to 20th	Night	10% 4 1 5% 3 4 4 3 5% 7% 53%	1967
	21st to end	Night	11% 6% 2 5% 3 4 5% 3 5% 7% 48%	2090
October	1st to 10th	Night	11% 6% 3 5% 4 4 4 3 4 5% 52%	2191
	11th to 20th	Night	16% 8% 2 6% 3 3 3 3 4 6% 45%	2280
	21st to end	Night	19% 10% 3 6% 4 4 4 3 5% 6% 37%	2693
November	1st to 10th	Night	12% 8% 2 6% 3 3 4 3 4 6% 48%	2536
	11th to 20th	Night	15% 11% 4 8% 4 4 4 4 5% 6% 35%	2600
	21st to end	Night	16% 12% 4 8% 5% 3 4 3 5% 5% 36%	2728
December	1st to 10th	Night	15% 11% 4 9% 5% 5% 4 4 5% 7% 32%	2779
	11th to 20th	Night	14% 13% 5% 10% 4 4 4 4 5% 6% 31%	3279
	21st to end	Night	21% 17% 7% 11% 5% 5% 5% 4 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	62% 5% 10% 16% 6%	2528
	11th to 20th	Day	60% 5% 14% 12% 9%	2530
	21st to end	Day	67% 5% 9% 13% 5%	2919
February	1st to 10th	Day	57% 6% 12% 15% 9% 1	1710
	11th to 20th	Day	48% 6% 11% 23% 10% 2	1845
	21st to end	Day	54% 6% 10% 20% 9% 1	1570
March	1st to 10th	Day	46% 6% 11% 22% 11% 3	3120
	11th to 20th	Day	40% 7% 12% 30% 10% 1	3309
	21st to end	Day	64% 8% 12% 13% 3 1	4155
April	1st to 10th	Day	54% 6% 10% 21% 9%	2280
	11th to 20th	Day	48% 7% 10% 21% 12% 2	2254
	21st to end	Day	51% 6% 12% 17% 13% 1	2346
May	1st to 10th	Day	45% 8% 11% 22% 14% 1	4136
	11th to 20th	Day	40% 7% 11% 28% 15%	4403
	21st to end	Day	37% 8% 12% 21% 16% 5%	4837
June	1st to 10th	Day	34% 8% 14% 26% 17% 2	2660
	11th to 20th	Day	33% 7% 13% 25% 20% 2	2660
	21st to end	Day	40% 9% 13% 23% 13% 2	2660
July	1st to 10th	Day	44% 8% 13% 23% 10% 2	4371
	11th to 20th	Day	28% 8% 18% 29% 17% 1	4365
	21st to end	Day	37% 9% 16% 17% 18% 3	4662
August	1st to 10th	Day	35% 8% 16% 28% 12% 1	4349
	11th to 20th	Day	32% 7% 13% 34% 14% 1	3765
	21st to end	Day	33% 7% 12% 30% 17% 2	4179
September	1st to 10th	Day	35% 6% 11% 26% 18% 3	2280
	11th to 20th	Day	30% 6% 12% 30% 21% 2	2193
	21st to end	Day	37% 5% 11% 27% 18% 1	2090
October	1st to 10th	Day	25% 4 7% 33% 30% 1	3298
	11th to 20th	Day	32% 5% 11% 26% 25% 1	3140
	21st to end	Day	43% 4 9% 27% 13% 3	3115
November	1st to 10th	Day	41% 4 14% 24% 15% 2	1762
	11th to 20th	Day	54% 4 11% 20% 10% 1	1800
	21st to end	Day	53% 4 12% 22% 8%	1670
December	1st to 10th	Day	53% 6% 13% 19% 8% 1	1584
	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	57% 5% 10% 18% 9% 1	4428
	11th to 20th	Night	65% 5% 10% 12% 8%	4440
	21st to end	Night	67% 5% 9% 13% 6% 1	4746
February	1st to 10th	Night	54% 4 10% 18% 13% 2	2470
	11th to 20th	Night	47% 5% 11% 22% 14% 1	2230
	21st to end	Night	51% 4 11% 20% 11% 4	1884
March	1st to 10th	Night	46% 5% 13% 22% 11% 4	3733
	11th to 20th	Night	35% 6% 11% 28% 18% 2	3682
	21st to end	Night	60% 6% 8% 19% 6% 1	3476
April	1st to 10th	Night	46% 6% 11% 22% 14% 2	1900
	11th to 20th	Night	46% 6% 7% 21% 17% 4	1875
	21st to end	Night	44% 7% 11% 23% 11% 3	1831
May	1st to 10th	Night	44% 8% 12% 18% 15% 3	2822
	11th to 20th	Night	38% 9% 15% 25% 12% 1	2507
	21st to end	Night	35% 9% 12% 20% 21% 3	2751
June	1st to 10th	Night	32% 7% 14% 25% 19% 3	1520
	11th to 20th	Night	33% 6% 11% 24% 23% 3	1520
	21st to end	Night	38% 8% 13% 21% 18% 2	1520
July	1st to 10th	Night	42% 7% 15% 19% 12% 4	2490
	11th to 20th	Night	26% 7% 15% 31% 19% 1	2482
	21st to end	Night	33% 10% 14% 18% 21% 3	2662
August	1st to 10th	Night	28% 9% 14% 30% 18% 2	2563
	11th to 20th	Night	31% 8% 14% 30% 17% 1	3130
	21st to end	Night	29% 6% 14% 31% 18% 3	3476
September	1st to 10th	Night	30% 6% 10% 27% 24% 3	1900
	11th to 20th	Night	29% 6% 8% 32% 22% 2	1967
	21st to end	Night	34% 6% 11% 30% 17% 2	2090
October	1st to 10th	Night	23% 4 7% 36% 29% 2	3659
	11th to 20th	Night	35% 4 8% 24% 27% 3	3779
	21st to end	Night	42% 4 9% 25% 18% 3	4431
November	1st to 10th	Night	38% 5% 9% 27% 18% 3	2536
	11th to 20th	Night	48% 5% 11% 21% 12% 2	2600
	21st to end	Night	50% 4 11% 22% 11% 1	2728
December	1st to 10th	Night	52% 6% 12% 21% 8% 1	2779
	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	23% 11% 42% 20% 3 1	270
	21st to end	Day	24% 11% 35% 25% 4 1	297
February	1st to 10th	Day	19% 17% 37% 21% 6%	270
	11th to 20th	Day	23% 16% 33% 23% 4	270
	21st to end	Day	23% 21% 38% 16% 2	225
March	1st to 10th	Day	17% 22% 39% 19% 3	270
	11th to 20th	Day	23% 17% 37% 14% 9% 1	270
	21st to end	Day	27% 14% 31% 19% 7% 2	496
April	1st to 10th	Day	25% 12% 35% 23% 5%	460
	11th to 20th	Day	21% 20% 27% 19% 10% 3	452
	21st to end	Day	23% 13% 30% 22% 9% 2	460
May	1st to 10th	Day	19% 14% 30% 24% 9% 3	466
	11th to 20th	Day	21% 10% 29% 26% 12% 3	675
	21st to end	Day	16% 9% 28% 25% 16% 6%	734
June	1st to 10th	Day	9% 8% 31% 28% 18% 6%	680
	11th to 20th	Day	10% 6% 32% 31% 15% 5%	680
	21st to end	Day	12% 8% 30% 31% 14% 5%	680
July	1st to 10th	Day	9% 3 20% 28% 25% 15%	671
	11th to 20th	Day	9% 5% 24% 33% 20% 10%	668
	21st to end	Day	7% 3 21% 37% 23% 8%	739
August	1st to 10th	Day	9% 3 20% 32% 25% 11%	676
	11th to 20th	Day	11% 5% 17% 27% 23% 17%	479
	21st to end	Day	8% 4 16% 32% 28% 12%	539
September	1st to 10th	Day	12% 7% 20% 30% 24% 7%	490
	11th to 20th	Day	9% 3 20% 29% 26% 13%	490
	21st to end	Day	14% 12% 24% 24% 18% 7%	490
October	1st to 10th	Day	14% 9% 29% 25% 18% 5%	386
	11th to 20th	Day	21% 20% 31% 21% 8%	300
	21st to end	Day	30% 13% 30% 22% 5% 1	330
November	1st to 10th	Day	16% 15% 35% 21% 10% 2	300
	11th to 20th	Day	22% 17% 36% 17% 7% 1	300
	21st to end	Day	23% 11% 39% 21% 6%	300
December	1st to 10th	Day	17% 15% 42% 19% 6% 1	294
	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	950
	21st to end	Night	21% 10% 35% 29% 5%	1045
February	1st to 10th	Night	23% 10% 39% 23% 5%	950
	11th to 20th	Night	19% 12% 37% 27% 5%	754
	21st to end	Night	22% 12% 41% 21% 4	628
March	1st to 10th	Night	22% 11% 37% 24% 6%	760
	11th to 20th	Night	15% 11% 38% 30% 6%	694
	21st to end	Night	23% 11% 34% 25% 7% 1	627
April	1st to 10th	Night	21% 13% 36% 24% 4	570
	11th to 20th	Night	22% 13% 31% 28% 6%	563
	21st to end	Night	19% 10% 35% 27% 8%	570
May	1st to 10th	Night	18% 8% 34% 31% 8% 1	570
	11th to 20th	Night	17% 7% 32% 32% 12%	561
	21st to end	Night	14% 5% 28% 35% 18%	617
June	1st to 10th	Night	9% 5% 29% 42% 15%	570
	11th to 20th	Night	10% 4 31% 43% 11% 1	570
	21st to end	Night	9% 4 29% 38% 19% 1	570
July	1st to 10th	Night	9% 2 16% 39% 31% 3	555
	11th to 20th	Night	8% 2 22% 40% 24% 4	552
	21st to end	Night	6% 1 19% 46% 25% 2	624
August	1st to 10th	Night	5% 3 13% 47% 28% 4	567
	11th to 20th	Night	7% 3 15% 41% 30% 5%	564
	21st to end	Night	8% 2 17% 41% 29% 3	627
September	1st to 10th	Night	11% 3 21% 35% 26% 4	570
	11th to 20th	Night	10% 5% 19% 35% 28% 3	637
	21st to end	Night	12% 8% 25% 33% 19% 3	760
October	1st to 10th	Night	13% 6% 28% 34% 17% 1	760
	11th to 20th	Night	20% 11% 31% 27% 10%	760
	21st to end	Night	25% 12% 32% 23% 8%	836
November	1st to 10th	Night	17% 11% 38% 23% 10% 1	780
	11th to 20th	Night	20% 14% 35% 24% 7%	800
	21st to end	Night	19% 13% 38% 24% 5%	928
December	1st to 10th	Night	20% 12% 38% 24% 5%	993
	11th to 20th	Night	22% 11% 35% 26% 4 1	950
	21st to end	Night	27% 14% 34% 21% 3	1045

Page generated at 2024-12-06 02:54:47. Version ac07

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