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 2024-01-14.

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	10% 12% 6% 11% 9% 5% 6% 6% 6% 7% 22%	74422
	Night	7% 13% 6% 11% 10% 5% 7% 6% 6% 7% 20%	75337
Transparency	Day	59% 10% 14% 13% 4	74058
	Night	60% 10% 13% 12% 4	75220
Seeing	Day	15% 11% 24% 26% 18% 5%	15998
	Night	14% 7% 22% 32% 21% 4	22610

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	5% 13% 8% 15% 14% 6% 7% 6% 6% 5% 15%	825
	11th to 20th	Day	7% 17% 7% 17% 10% 6% 7% 6% 7% 6% 10%	1098
	21st to end	Day	6% 16% 8% 13% 9% 7% 7% 5% 7% 8% 15%	1188
February	1st to 10th	Day	5% 12% 6% 14% 7% 4 6% 8% 6% 11% 23%	1291
	11th to 20th	Day	5% 17% 7% 11% 8% 6% 7% 7% 6% 9% 18%	1400
	21st to end	Day	2 11% 8% 11% 9% 6% 7% 7% 6% 9% 25%	1274
March	1st to 10th	Day	3 10% 6% 12% 9% 6% 7% 6% 8% 7% 25%	1800
	11th to 20th	Day	2 13% 8% 14% 10% 5% 9% 6% 6% 9% 19%	1836
	21st to end	Day	2 11% 9% 14% 11% 5% 7% 5% 6% 8% 23%	2376
April	1st to 10th	Day	4 15% 8% 14% 9% 4 5% 6% 7% 8% 20%	2203
	11th to 20th	Day	4 14% 8% 12% 10% 5% 6% 5% 6% 7% 23%	2448
	21st to end	Day	5% 14% 6% 10% 10% 5% 7% 6% 6% 7% 25%	2555
May	1st to 10th	Day	10% 14% 6% 10% 9% 5% 6% 5% 6% 7% 21%	2772
	11th to 20th	Day	9% 15% 5% 8% 8% 4 6% 5% 7% 6% 27%	2833
	21st to end	Day	10% 10% 4 9% 8% 5% 6% 6% 6% 7% 29%	3259
June	1st to 10th	Day	14% 11% 5% 10% 9% 5% 6% 6% 6% 6% 22%	3197
	11th to 20th	Day	15% 11% 5% 10% 9% 4 7% 6% 6% 7% 20%	3240
	21st to end	Day	11% 8% 4 9% 10% 5% 7% 7% 7% 9% 23%	3240
July	1st to 10th	Day	13% 9% 4 9% 7% 5% 7% 7% 7% 7% 25%	3240
	11th to 20th	Day	17% 10% 5% 10% 9% 4 7% 7% 7% 7% 16%	3030
	21st to end	Day	14% 9% 4 9% 8% 5% 6% 6% 6% 8% 26%	3135
August	1st to 10th	Day	12% 9% 4 9% 6% 5% 6% 6% 6% 8% 29%	2847
	11th to 20th	Day	18% 11% 5% 9% 8% 4 5% 5% 5% 6% 22%	2476
	21st to end	Day	20% 11% 5% 8% 6% 5% 6% 6% 5% 7% 22%	2752
September	1st to 10th	Day	18% 12% 5% 11% 7% 4 6% 6% 5% 5% 20%	2226
	11th to 20th	Day	13% 9% 4 9% 8% 4 6% 6% 6% 8% 27%	2134
	21st to end	Day	15% 14% 6% 11% 9% 4 6% 6% 5% 5% 19%	1957
October	1st to 10th	Day	14% 15% 5% 10% 7% 5% 5% 5% 5% 7% 21%	1764
	11th to 20th	Day	13% 16% 5% 11% 10% 5% 6% 5% 5% 6% 18%	1620
	21st to end	Day	8% 13% 6% 13% 10% 5% 7% 6% 6% 6% 18%	1584
November	1st to 10th	Day	7% 16% 8% 14% 11% 6% 4 8% 5% 8% 14%	1302
	11th to 20th	Day	7% 15% 8% 15% 13% 5% 7% 6% 5% 7% 11%	1216
	21st to end	Day	5% 14% 8% 15% 11% 7% 5% 7% 10% 6% 12%	969
December	1st to 10th	Day	7% 12% 6% 14% 12% 8% 9% 7% 7% 7% 11%	950
	11th to 20th	Day	4 13% 7% 11% 9% 5% 8% 7% 9% 9% 18%	999
	21st to end	Day	6% 17% 6% 13% 9% 6% 6% 8% 8% 6% 15%	1386
January	1st to 10th	Night	5% 14% 8% 14% 13% 6% 8% 5% 6% 6% 15%	3357
	11th to 20th	Night	8% 16% 8% 14% 10% 5% 6% 6% 7% 8% 14%	2934
	21st to end	Night	6% 15% 7% 14% 10% 6% 7% 6% 6% 7% 16%	3168
February	1st to 10th	Night	5% 13% 6% 12% 9% 4 7% 7% 7% 9% 19%	2667
	11th to 20th	Night	4 15% 7% 12% 11% 6% 7% 7% 7% 8% 17%	2447
	21st to end	Night	3 11% 7% 11% 9% 5% 6% 5% 6% 8% 29%	1979
March	1st to 10th	Night	4 10% 7% 12% 8% 5% 7% 6% 5% 7% 29%	2160
	11th to 20th	Night	1 11% 10% 13% 11% 6% 8% 6% 6% 6% 20%	2122
	21st to end	Night	2 11% 7% 13% 10% 7% 6% 7% 6% 7% 23%	1980
April	1st to 10th	Night	3 10% 5% 13% 9% 6% 7% 7% 7% 7% 27%	1757
	11th to 20th	Night	4 10% 5% 9% 8% 5% 6% 6% 8% 8% 31%	1459
	21st to end	Night	5% 12% 5% 8% 7% 6% 8% 6% 7% 8% 28%	1405
May	1st to 10th	Night	9% 9% 5% 9% 7% 4 6% 7% 8% 8% 27%	1188
	11th to 20th	Night	7% 9% 3 7% 8% 4 6% 6% 5% 9% 35%	1062
	21st to end	Night	7% 7% 4 7% 5% 3 7% 6% 8% 9% 36%	1014
June	1st to 10th	Night	9% 6% 3 6% 9% 4 6% 7% 8% 9% 32%	761
	11th to 20th	Night	13% 9% 5% 6% 8% 4 5% 7% 6% 10% 28%	720
	21st to end	Night	9% 7% 2 6% 7% 4 7% 8% 8% 9% 31%	720
July	1st to 10th	Night	11% 6% 4 8% 6% 5% 6% 7% 8% 11% 29%	720
	11th to 20th	Night	13% 9% 5% 8% 9% 6% 8% 8% 6% 11% 18%	929
	21st to end	Night	11% 8% 3 8% 7% 4 5% 5% 8% 10% 30%	1182
August	1st to 10th	Night	10% 7% 3 8% 7% 4 4 8% 9% 10% 30%	1090
	11th to 20th	Night	14% 8% 3 8% 8% 4 6% 7% 7% 9% 26%	1424
	21st to end	Night	18% 11% 5% 8% 7% 3 6% 5% 5% 6% 25%	1604
September	1st to 10th	Night	14% 12% 4 8% 7% 4 6% 6% 6% 7% 26%	1732
	11th to 20th	Night	10% 8% 4 8% 8% 4 6% 5% 6% 7% 34%	1826
	21st to end	Night	15% 15% 5% 9% 8% 5% 6% 5% 6% 6% 21%	2002
October	1st to 10th	Night	13% 14% 5% 9% 7% 4 5% 6% 6% 6% 25%	2196
	11th to 20th	Night	13% 20% 5% 9% 8% 4 6% 5% 5% 6% 19%	2340
	21st to end	Night	7% 18% 6% 11% 9% 5% 6% 5% 5% 7% 21%	2770
November	1st to 10th	Night	7% 14% 8% 12% 11% 6% 8% 7% 6% 7% 14%	2776
	11th to 20th	Night	7% 15% 8% 14% 11% 5% 8% 8% 7% 6% 12%	2962
	21st to end	Night	7% 17% 8% 15% 12% 5% 6% 7% 6% 6% 12%	3192
December	1st to 10th	Night	6% 16% 8% 14% 13% 6% 7% 7% 6% 7% 9%	3230
	11th to 20th	Night	5% 15% 7% 14% 12% 6% 7% 5% 7% 7% 15%	4192
	21st to end	Night	7% 16% 6% 11% 10% 6% 7% 8% 6% 6% 16%	6270

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	68% 8% 9% 7% 7% 1	825
	11th to 20th	Day	70% 9% 10% 7% 4	1098
	21st to end	Day	64% 10% 12% 9% 5%	1188
February	1st to 10th	Day	54% 8% 12% 15% 9% 2	1291
	11th to 20th	Day	62% 8% 14% 10% 6% 1	1408
	21st to end	Day	53% 10% 15% 15% 5% 1	1274
March	1st to 10th	Day	55% 9% 12% 16% 7% 2	1800
	11th to 20th	Day	61% 9% 14% 11% 5%	1836
	21st to end	Day	59% 10% 13% 10% 7% 1	2376
April	1st to 10th	Day	60% 10% 16% 10% 3	2203
	11th to 20th	Day	59% 9% 13% 14% 4	2448
	21st to end	Day	55% 11% 16% 14% 4	2555
May	1st to 10th	Day	58% 11% 17% 12% 2	2772
	11th to 20th	Day	52% 10% 13% 19% 6%	2836
	21st to end	Day	50% 10% 16% 19% 5%	3260
June	1st to 10th	Day	61% 9% 12% 14% 4	3197
	11th to 20th	Day	60% 10% 14% 14% 2	3240
	21st to end	Day	55% 13% 16% 13% 3	3240
July	1st to 10th	Day	53% 13% 16% 14% 4	3151
	11th to 20th	Day	64% 13% 15% 7%	2934
	21st to end	Day	55% 12% 18% 14% 2	2961
August	1st to 10th	Day	52% 11% 21% 14% 2	2828
	11th to 20th	Day	61% 10% 16% 11% 1	2476
	21st to end	Day	62% 11% 17% 9% 1	2752
September	1st to 10th	Day	64% 11% 12% 10% 3	2226
	11th to 20th	Day	54% 10% 15% 17% 3	2134
	21st to end	Day	65% 10% 12% 11% 2	1957
October	1st to 10th	Day	63% 8% 15% 12% 2	1764
	11th to 20th	Day	66% 10% 13% 10% 1	1620
	21st to end	Day	63% 11% 13% 11% 2	1584
November	1st to 10th	Day	67% 11% 12% 9% 2	1302
	11th to 20th	Day	71% 7% 10% 10% 1	1216
	21st to end	Day	65% 11% 11% 8% 5%	969
December	1st to 10th	Day	67% 11% 11% 8% 2	950
	11th to 20th	Day	57% 8% 10% 17% 8%	1001
	21st to end	Day	62% 11% 8% 13% 5% 1	1386
January	1st to 10th	Night	68% 9% 9% 7% 6% 1	3357
	11th to 20th	Night	68% 8% 10% 9% 5%	2934
	21st to end	Night	64% 10% 10% 12% 4	3168
February	1st to 10th	Night	59% 8% 9% 13% 9% 2	2667
	11th to 20th	Night	62% 9% 13% 10% 5% 1	2450
	21st to end	Night	51% 9% 17% 15% 7% 1	1979
March	1st to 10th	Night	52% 8% 11% 18% 7% 3	2160
	11th to 20th	Night	61% 9% 12% 13% 5% 1	2124
	21st to end	Night	58% 9% 15% 10% 8%	1980
April	1st to 10th	Night	52% 9% 17% 17% 5%	1757
	11th to 20th	Night	48% 12% 17% 18% 5%	1459
	21st to end	Night	51% 10% 16% 19% 4	1405
May	1st to 10th	Night	50% 12% 21% 13% 3	1188
	11th to 20th	Night	45% 9% 15% 23% 7% 1	1062
	21st to end	Night	42% 7% 20% 25% 7%	1014
June	1st to 10th	Night	47% 12% 18% 19% 3	761
	11th to 20th	Night	51% 10% 18% 17% 3	720
	21st to end	Night	44% 16% 21% 17% 2	720
July	1st to 10th	Night	47% 12% 20% 16% 5%	700
	11th to 20th	Night	56% 16% 18% 10%	902
	21st to end	Night	47% 11% 24% 17% 1	1116
August	1st to 10th	Night	43% 15% 24% 16% 3	1084
	11th to 20th	Night	50% 14% 16% 17% 2	1424
	21st to end	Night	60% 10% 17% 12%	1604
September	1st to 10th	Night	55% 12% 18% 14% 1	1732
	11th to 20th	Night	47% 11% 19% 20% 3	1826
	21st to end	Night	63% 9% 11% 13% 3	2002
October	1st to 10th	Night	57% 13% 16% 12% 3	2196
	11th to 20th	Night	65% 10% 14% 9% 1	2340
	21st to end	Night	61% 10% 14% 12% 2	2770
November	1st to 10th	Night	66% 11% 12% 9% 1	2776
	11th to 20th	Night	68% 10% 10% 10% 2	2962
	21st to end	Night	70% 8% 10% 9% 2	3192
December	1st to 10th	Night	70% 10% 9% 8% 2	3230
	11th to 20th	Night	66% 7% 10% 10% 6%	4189
	21st to end	Night	61% 11% 8% 10% 8% 2	6270

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% 15% 39% 27% 6%	103
	11th to 20th	Day	14% 5% 18% 28% 25% 10%	166
	21st to end	Day	13% 15% 21% 22% 23% 6%	176
February	1st to 10th	Day	12% 6% 23% 34% 21% 5%	307
	11th to 20th	Day	11% 11% 30% 27% 15% 7%	335
	21st to end	Day	8% 11% 29% 31% 15% 7%	280
March	1st to 10th	Day	7% 11% 28% 31% 14% 8%	340
	11th to 20th	Day	7% 11% 33% 27% 20% 2	348
	21st to end	Day	7% 12% 27% 29% 19% 5%	462
April	1st to 10th	Day	10% 16% 29% 25% 17% 4	420
	11th to 20th	Day	9% 12% 26% 30% 18% 4	552
	21st to end	Day	12% 14% 28% 28% 15% 3	600
May	1st to 10th	Day	14% 15% 28% 26% 14% 3	603
	11th to 20th	Day	14% 12% 24% 25% 17% 7%	625
	21st to end	Day	12% 10% 24% 26% 22% 5%	828
June	1st to 10th	Day	16% 10% 23% 26% 21% 4	810
	11th to 20th	Day	18% 8% 24% 27% 20% 4	810
	21st to end	Day	13% 8% 21% 30% 22% 6%	810
July	1st to 10th	Day	16% 8% 18% 28% 24% 6%	796
	11th to 20th	Day	20% 10% 19% 24% 21% 6%	695
	21st to end	Day	16% 11% 19% 24% 21% 9%	684
August	1st to 10th	Day	16% 8% 23% 26% 18% 8%	626
	11th to 20th	Day	26% 14% 24% 21% 11% 4	615
	21st to end	Day	23% 10% 22% 26% 15% 4	673
September	1st to 10th	Day	24% 15% 23% 20% 14% 4	450
	11th to 20th	Day	15% 13% 25% 22% 19% 6%	450
	21st to end	Day	26% 16% 27% 20% 9% 2	438
October	1st to 10th	Day	25% 16% 27% 21% 10% 2	360
	11th to 20th	Day	24% 15% 29% 20% 9% 3	360
	21st to end	Day	12% 9% 23% 33% 19% 4	350
November	1st to 10th	Day	13% 11% 27% 29% 16% 5%	180
	11th to 20th	Day	11% 7% 24% 33% 14% 11%	180
	21st to end	Day	13% 10% 24% 29% 15% 9%	180
December	1st to 10th	Day	10% 6% 21% 36% 19% 7%	180
	11th to 20th	Day	7% 7% 23% 27% 27% 7%	107
	21st to end	Day	8% 12% 17% 29% 23% 10%	99
January	1st to 10th	Night	12% 4 25% 34% 21% 4	1020
	11th to 20th	Night	15% 7% 25% 32% 18% 2	817
	21st to end	Night	12% 9% 26% 34% 15% 3	880
February	1st to 10th	Night	11% 6% 23% 39% 18% 2	800
	11th to 20th	Night	10% 8% 27% 35% 17% 2	784
	21st to end	Night	7% 6% 27% 38% 18% 4	652
March	1st to 10th	Night	7% 7% 24% 33% 26% 3	720
	11th to 20th	Night	6% 7% 27% 31% 26% 3	702
	21st to end	Night	6% 6% 19% 34% 26% 9%	594
April	1st to 10th	Night	8% 6% 17% 32% 32% 6%	540
	11th to 20th	Night	6% 7% 21% 34% 29% 4	533
	21st to end	Night	10% 6% 22% 29% 29% 5%	505
May	1st to 10th	Night	12% 6% 21% 31% 25% 5%	360
	11th to 20th	Night	13% 5% 19% 29% 31% 3	354
	21st to end	Night	9% 4 20% 28% 35% 4	389
June	1st to 10th	Night	12% 3 18% 35% 31% 1	221
	11th to 20th	Night	18% 2 18% 32% 27% 3	180
	21st to end	Night	12% 4 16% 29% 37% 1	180
July	1st to 10th	Night	14% 2 16% 29% 37% 2	175
	11th to 20th	Night	14% 7% 18% 30% 26% 4	284
	21st to end	Night	13% 4 20% 28% 28% 6%	394
August	1st to 10th	Night	13% 5% 20% 28% 31% 4	358
	11th to 20th	Night	19% 8% 20% 29% 19% 5%	534
	21st to end	Night	25% 4 18% 27% 23% 3	594
September	1st to 10th	Night	20% 6% 21% 30% 20% 3	540
	11th to 20th	Night	14% 6% 20% 29% 26% 5%	566
	21st to end	Night	26% 9% 23% 27% 13% 3	720
October	1st to 10th	Night	22% 10% 22% 29% 15% 2	720
	11th to 20th	Night	25% 9% 19% 29% 15% 2	720
	21st to end	Night	16% 9% 22% 33% 16% 4	868
November	1st to 10th	Night	14% 6% 24% 37% 16% 3	830
	11th to 20th	Night	13% 7% 21% 32% 23% 5%	850
	21st to end	Night	14% 8% 25% 33% 16% 4	1002
December	1st to 10th	Night	13% 8% 25% 33% 19% 2	1040
	11th to 20th	Night	13% 6% 21% 38% 18% 4	1040
	21st to end	Night	14% 8% 23% 31% 18% 5%	1144

Page generated at 2024-01-11 02:22:41. Version ac07

Copyright 2024 Attilla Danko