Johnsons Crossing
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Johnsons Crossing clear sky chart from 2005-11-06 to 2026-01-02.

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	8% 12% 5% 12% 7% 7% 6% 5% 7% 7% 23%	131770
	Night	6% 13% 5% 13% 8% 7% 6% 5% 7% 8% 21%	128195
Transparency	Day	55% 11% 15% 15% 5%	131418
	Night	56% 10% 13% 14% 6%	128125
Seeing	Day	15% 12% 24% 26% 18% 5%	18697
	Night	13% 7% 23% 32% 21% 4	25160

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	3 12% 6% 18% 13% 9% 7% 5% 5% 4 19%	1964
	11th to 20th	Day	3 12% 6% 17% 10% 9% 7% 5% 6% 7% 19%	2702
	21st to end	Day	5% 16% 5% 13% 7% 7% 6% 4 6% 7% 24%	2992
February	1st to 10th	Day	4 13% 5% 13% 7% 6% 7% 6% 6% 11% 22%	1435
	11th to 20th	Day	4 18% 6% 12% 7% 7% 6% 5% 7% 9% 19%	1560
	21st to end	Day	2 13% 6% 13% 8% 7% 7% 5% 6% 9% 24%	1422
March	1st to 10th	Day	2 8% 4 14% 9% 9% 8% 6% 7% 6% 26%	4496
	11th to 20th	Day	2 14% 6% 14% 8% 7% 8% 5% 7% 8% 21%	4630
	21st to end	Day	1 9% 6% 14% 8% 7% 6% 5% 7% 9% 27%	5969
April	1st to 10th	Day	3 15% 7% 16% 8% 6% 6% 5% 7% 8% 20%	2449
	11th to 20th	Day	3 14% 6% 13% 9% 7% 6% 4 6% 7% 24%	2724
	21st to end	Day	4 15% 5% 11% 8% 6% 7% 4 6% 7% 25%	2839
May	1st to 10th	Day	10% 14% 5% 11% 7% 7% 6% 4 6% 7% 25%	6964
	11th to 20th	Day	6% 17% 5% 13% 8% 6% 7% 4 7% 7% 19%	7193
	21st to end	Day	8% 10% 4 11% 7% 7% 7% 6% 7% 7% 26%	8307
June	1st to 10th	Day	13% 12% 4 11% 8% 7% 5% 5% 6% 7% 22%	3553
	11th to 20th	Day	13% 11% 4 11% 7% 6% 6% 5% 6% 8% 22%	3600
	21st to end	Day	11% 8% 4 10% 8% 7% 7% 6% 8% 9% 23%	3600
July	1st to 10th	Day	11% 8% 3 10% 6% 7% 7% 6% 8% 8% 26%	8160
	11th to 20th	Day	12% 11% 4 11% 8% 6% 7% 5% 7% 8% 20%	7600
	21st to end	Day	11% 8% 3 10% 8% 7% 7% 6% 8% 9% 24%	7876
August	1st to 10th	Day	8% 7% 3 8% 5% 5% 5% 4 6% 7% 45%	5151
	11th to 20th	Day	15% 9% 3 8% 5% 5% 5% 4 6% 9% 33%	4480
	21st to end	Day	17% 11% 4 9% 5% 6% 6% 5% 6% 8% 24%	4978
September	1st to 10th	Day	16% 12% 4 12% 6% 6% 6% 4 6% 6% 22%	2472
	11th to 20th	Day	12% 10% 4 11% 6% 5% 6% 5% 6% 7% 27%	2370
	21st to end	Day	14% 15% 6% 13% 7% 6% 6% 4 5% 5% 20%	2173
October	1st to 10th	Day	11% 16% 5% 10% 7% 8% 7% 5% 7% 7% 17%	3193
	11th to 20th	Day	8% 15% 6% 14% 6% 5% 5% 4 6% 6% 24%	2933
	21st to end	Day	6% 18% 5% 15% 8% 8% 7% 5% 7% 6% 15%	2829
November	1st to 10th	Day	7% 16% 7% 16% 10% 7% 5% 6% 6% 7% 14%	1442
	11th to 20th	Day	6% 18% 6% 17% 11% 7% 6% 5% 5% 7% 11%	1344
	21st to end	Day	5% 14% 8% 16% 9% 8% 6% 5% 10% 7% 12%	1071
December	1st to 10th	Day	6% 17% 6% 16% 8% 8% 7% 6% 8% 7% 12%	1680
	11th to 20th	Day	3 10% 6% 18% 12% 7% 7% 5% 9% 8% 16%	1595
	21st to end	Day	5% 15% 6% 17% 10% 8% 7% 5% 6% 8% 13%	2024
January	1st to 10th	Night	3 13% 6% 18% 11% 12% 8% 3 5% 6% 14%	8034
	11th to 20th	Night	4 14% 6% 13% 7% 6% 6% 6% 7% 9% 23%	7196
	21st to end	Night	6% 16% 6% 15% 8% 7% 6% 5% 7% 7% 18%	7964
February	1st to 10th	Night	4 14% 5% 13% 8% 6% 7% 5% 8% 9% 19%	2963
	11th to 20th	Night	3 15% 6% 13% 9% 8% 7% 5% 7% 7% 20%	2727
	21st to end	Night	3 12% 5% 13% 9% 6% 6% 4 7% 7% 28%	2205
March	1st to 10th	Night	2 8% 4 12% 8% 8% 8% 7% 8% 10% 25%	5378
	11th to 20th	Night	3 13% 6% 12% 10% 9% 7% 5% 7% 9% 21%	5334
	21st to end	Night	1 10% 6% 14% 7% 7% 8% 6% 8% 9% 25%	4984
April	1st to 10th	Night	3 10% 5% 14% 7% 7% 7% 5% 8% 7% 27%	1951
	11th to 20th	Night	3 11% 4 10% 7% 6% 6% 5% 8% 8% 32%	1623
	21st to end	Night	4 12% 4 10% 7% 8% 6% 4 7% 8% 28%	1561
May	1st to 10th	Night	5% 10% 4 11% 6% 6% 5% 5% 7% 8% 32%	2996
	11th to 20th	Night	5% 11% 5% 13% 9% 7% 7% 5% 7% 8% 23%	2702
	21st to end	Night	6% 7% 3 8% 6% 5% 7% 6% 8% 9% 35%	2566
June	1st to 10th	Night	8% 6% 3 7% 8% 6% 7% 5% 8% 9% 31%	845
	11th to 20th	Night	11% 10% 4 7% 7% 5% 6% 5% 6% 10% 28%	800
	21st to end	Night	9% 8% 2 6% 8% 5% 8% 6% 9% 10% 31%	800
July	1st to 10th	Night	9% 7% 3 8% 6% 6% 6% 6% 8% 11% 31%	1800
	11th to 20th	Night	10% 10% 4 9% 6% 6% 6% 4 6% 10% 28%	2359
	21st to end	Night	15% 7% 3 8% 6% 6% 6% 5% 8% 9% 27%	2967
August	1st to 10th	Night	8% 5% 2 6% 5% 3 4 5% 7% 8% 47%	1998
	11th to 20th	Night	11% 7% 3 7% 5% 4 5% 4 7% 10% 36%	2578
	21st to end	Night	14% 12% 5% 12% 7% 6% 6% 5% 5% 5% 24%	2931
September	1st to 10th	Night	13% 11% 3 9% 6% 6% 6% 5% 6% 7% 27%	1925
	11th to 20th	Night	9% 9% 4 9% 7% 6% 5% 4 6% 7% 35%	2030
	21st to end	Night	14% 15% 5% 11% 7% 7% 6% 4 6% 6% 20%	2225
October	1st to 10th	Night	10% 14% 4 10% 7% 6% 6% 5% 8% 9% 22%	3997
	11th to 20th	Night	10% 17% 6% 13% 7% 6% 6% 4 6% 6% 18%	4215
	21st to end	Night	7% 16% 4 13% 8% 6% 6% 5% 7% 8% 20%	4967
November	1st to 10th	Night	7% 15% 7% 14% 9% 8% 7% 6% 6% 7% 14%	3076
	11th to 20th	Night	6% 17% 8% 16% 9% 7% 8% 5% 6% 6% 12%	3274
	21st to end	Night	6% 16% 7% 18% 9% 7% 6% 5% 6% 6% 13%	3528
December	1st to 10th	Night	7% 20% 7% 15% 9% 7% 6% 4 5% 6% 13%	5720
	11th to 20th	Night	3 12% 6% 22% 11% 8% 6% 4 6% 7% 15%	6802
	21st to end	Night	5% 15% 7% 16% 9% 8% 7% 6% 6% 8% 14%	9174

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	65% 8% 7% 6% 13% 1	1964
	11th to 20th	Day	60% 9% 11% 8% 11% 1	2720
	21st to end	Day	56% 11% 12% 13% 7%	2992
February	1st to 10th	Day	53% 8% 12% 15% 10% 2	1435
	11th to 20th	Day	60% 8% 14% 11% 7% 1	1568
	21st to end	Day	52% 11% 15% 15% 6% 1	1422
March	1st to 10th	Day	51% 11% 12% 15% 10% 1	4496
	11th to 20th	Day	54% 11% 14% 12% 9%	4630
	21st to end	Day	47% 13% 15% 19% 6% 1	5969
April	1st to 10th	Day	59% 11% 15% 12% 3	2449
	11th to 20th	Day	57% 10% 13% 15% 6%	2724
	21st to end	Day	53% 12% 17% 14% 4	2839
May	1st to 10th	Day	53% 10% 12% 20% 5%	6964
	11th to 20th	Day	55% 12% 13% 16% 4	7196
	21st to end	Day	49% 11% 12% 20% 8%	8308
June	1st to 10th	Day	60% 9% 12% 15% 4	3553
	11th to 20th	Day	57% 10% 15% 15% 3	3600
	21st to end	Day	54% 13% 17% 13% 3	3600
July	1st to 10th	Day	50% 12% 19% 17% 2	8071
	11th to 20th	Day	58% 12% 18% 11%	7504
	21st to end	Day	52% 13% 22% 11% 1	7655
August	1st to 10th	Day	38% 8% 17% 21% 13% 2	5132
	11th to 20th	Day	47% 10% 20% 18% 5%	4522
	21st to end	Day	58% 10% 15% 16% 1	4977
September	1st to 10th	Day	61% 11% 13% 12% 3	2472
	11th to 20th	Day	54% 10% 14% 18% 4	2370
	21st to end	Day	64% 9% 12% 12% 2	2173
October	1st to 10th	Day	64% 9% 11% 14% 2	3193
	11th to 20th	Day	59% 8% 16% 16% 1	2933
	21st to end	Day	65% 12% 14% 8% 1	2829
November	1st to 10th	Day	67% 11% 11% 10% 1	1442
	11th to 20th	Day	71% 7% 10% 10% 2	1344
	21st to end	Day	63% 11% 12% 10% 5%	1071
December	1st to 10th	Day	62% 13% 15% 7% 3	1680
	11th to 20th	Day	57% 10% 14% 13% 6%	1597
	21st to end	Day	62% 12% 8% 14% 4	2024
January	1st to 10th	Night	69% 8% 6% 5% 11%	8034
	11th to 20th	Night	53% 11% 10% 12% 12% 2	7240
	21st to end	Night	61% 11% 11% 11% 5% 1	7964
February	1st to 10th	Night	57% 9% 9% 14% 9% 2	2963
	11th to 20th	Night	59% 10% 13% 11% 6% 1	2730
	21st to end	Night	51% 9% 17% 15% 7% 1	2205
March	1st to 10th	Night	46% 10% 13% 21% 8% 1	5378
	11th to 20th	Night	54% 10% 13% 14% 8%	5336
	21st to end	Night	48% 11% 14% 16% 10% 1	4984
April	1st to 10th	Night	51% 10% 17% 18% 5%	1951
	11th to 20th	Night	47% 11% 17% 18% 6% 1	1623
	21st to end	Night	49% 11% 17% 20% 4	1561
May	1st to 10th	Night	46% 10% 13% 25% 6%	2993
	11th to 20th	Night	49% 14% 15% 16% 6%	2702
	21st to end	Night	38% 10% 15% 28% 10%	2566
June	1st to 10th	Night	46% 13% 18% 20% 3	845
	11th to 20th	Night	49% 11% 19% 18% 4	800
	21st to end	Night	43% 16% 21% 18% 2	800
July	1st to 10th	Night	43% 11% 25% 19% 3	1780
	11th to 20th	Night	48% 12% 25% 13% 2	2332
	21st to end	Night	49% 12% 26% 13% 1	2883
August	1st to 10th	Night	32% 11% 19% 24% 13% 1	1992
	11th to 20th	Night	41% 11% 20% 22% 6%	2602
	21st to end	Night	61% 9% 13% 16% 2	2931
September	1st to 10th	Night	54% 12% 19% 14% 1	1925
	11th to 20th	Night	47% 11% 18% 21% 3	2030
	21st to end	Night	63% 9% 11% 13% 4	2225
October	1st to 10th	Night	55% 11% 15% 16% 2	3997
	11th to 20th	Night	65% 9% 12% 13% 1	4215
	21st to end	Night	58% 12% 16% 13% 2	4967
November	1st to 10th	Night	65% 11% 12% 10% 2	3076
	11th to 20th	Night	69% 10% 10% 10% 2	3274
	21st to end	Night	68% 8% 11% 10% 3	3528
December	1st to 10th	Night	68% 10% 10% 10% 2	5720
	11th to 20th	Night	63% 9% 12% 11% 5%	6799
	21st to end	Night	62% 11% 8% 11% 6% 1	9174

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	3 11% 16% 36% 26% 7%	116
	11th to 20th	Day	12% 7% 22% 29% 22% 9%	200
	21st to end	Day	14% 16% 20% 26% 20% 5%	220
February	1st to 10th	Day	11% 6% 22% 35% 22% 5%	364
	11th to 20th	Day	9% 10% 27% 28% 18% 7%	395
	21st to end	Day	8% 11% 28% 31% 15% 6%	331
March	1st to 10th	Day	6% 12% 27% 32% 16% 8%	400
	11th to 20th	Day	9% 12% 30% 26% 20% 3	410
	21st to end	Day	7% 11% 25% 29% 23% 5%	550
April	1st to 10th	Day	9% 15% 32% 25% 15% 3	500
	11th to 20th	Day	8% 13% 27% 29% 19% 4	648
	21st to end	Day	11% 13% 27% 29% 17% 4	700
May	1st to 10th	Day	15% 17% 27% 24% 13% 3	703
	11th to 20th	Day	13% 14% 25% 26% 16% 6%	725
	21st to end	Day	12% 11% 25% 26% 21% 5%	956
June	1st to 10th	Day	17% 11% 24% 25% 20% 4	930
	11th to 20th	Day	16% 8% 23% 28% 21% 5%	930
	21st to end	Day	12% 7% 19% 29% 24% 8%	930
July	1st to 10th	Day	16% 7% 20% 28% 23% 6%	916
	11th to 20th	Day	20% 10% 19% 24% 21% 6%	803
	21st to end	Day	15% 11% 20% 25% 20% 9%	794
August	1st to 10th	Day	15% 9% 22% 25% 21% 8%	726
	11th to 20th	Day	24% 15% 24% 21% 12% 4	715
	21st to end	Day	22% 11% 22% 27% 15% 4	780
September	1st to 10th	Day	21% 14% 23% 22% 15% 5%	530
	11th to 20th	Day	18% 13% 25% 21% 18% 6%	530
	21st to end	Day	25% 16% 25% 20% 11% 3	514
October	1st to 10th	Day	24% 17% 25% 22% 9% 2	420
	11th to 20th	Day	24% 16% 28% 20% 9% 2	420
	21st to end	Day	13% 11% 22% 32% 19% 3	410
November	1st to 10th	Day	13% 11% 27% 29% 15% 5%	220
	11th to 20th	Day	10% 8% 26% 31% 16% 9%	220
	21st to end	Day	11% 10% 21% 30% 20% 8%	220
December	1st to 10th	Day	10% 11% 21% 34% 19% 6%	220
	11th to 20th	Day	6% 7% 22% 28% 26% 11%	130
	21st to end	Day	7% 13% 17% 30% 23% 10%	121
January	1st to 10th	Night	12% 5% 25% 33% 22% 4	1085
	11th to 20th	Night	14% 9% 26% 32% 17% 2	900
	21st to end	Night	12% 11% 26% 34% 14% 3	990
February	1st to 10th	Night	11% 6% 22% 39% 19% 2	900
	11th to 20th	Night	9% 8% 27% 36% 19% 2	884
	21st to end	Night	7% 6% 28% 38% 18% 4	735
March	1st to 10th	Night	7% 7% 24% 33% 27% 3	800
	11th to 20th	Night	7% 7% 27% 30% 27% 3	779
	21st to end	Night	6% 5% 18% 34% 28% 8%	660
April	1st to 10th	Night	7% 5% 19% 34% 30% 5%	600
	11th to 20th	Night	6% 8% 21% 34% 27% 4	593
	21st to end	Night	9% 6% 21% 30% 29% 5%	561
May	1st to 10th	Night	11% 7% 22% 31% 25% 5%	400
	11th to 20th	Night	11% 5% 21% 31% 29% 3	394
	21st to end	Night	9% 4 21% 30% 33% 3	433
June	1st to 10th	Night	11% 4 18% 36% 29% 1	245
	11th to 20th	Night	17% 2 17% 34% 28% 3	200
	21st to end	Night	12% 5% 15% 28% 39% 3	200
July	1st to 10th	Night	13% 2 15% 31% 36% 2	195
	11th to 20th	Night	15% 7% 18% 29% 27% 4	317
	21st to end	Night	14% 5% 20% 29% 27% 6%	438
August	1st to 10th	Night	13% 4 20% 29% 31% 4	399
	11th to 20th	Night	19% 8% 19% 30% 19% 5%	594
	21st to end	Night	24% 4 18% 29% 22% 3	660
September	1st to 10th	Night	19% 6% 21% 31% 20% 3	600
	11th to 20th	Night	14% 7% 20% 30% 25% 5%	630
	21st to end	Night	25% 10% 23% 26% 13% 3	800
October	1st to 10th	Night	21% 11% 22% 30% 15% 2	800
	11th to 20th	Night	24% 10% 20% 30% 14% 2	800
	21st to end	Night	16% 9% 24% 32% 16% 4	974
November	1st to 10th	Night	14% 6% 25% 37% 15% 3	930
	11th to 20th	Night	12% 7% 21% 32% 23% 5%	950
	21st to end	Night	13% 7% 24% 34% 19% 3	1118
December	1st to 10th	Night	14% 9% 25% 32% 18% 2	1160
	11th to 20th	Night	12% 6% 20% 38% 19% 5%	1160
	21st to end	Night	13% 8% 24% 32% 18% 6%	1276

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