Medicine Hat
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Medicine Hat clear sky chart from 2005-11-06 to 2025-07-06.

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% 8% 3 7% 5% 4 5% 4 6% 8% 44%	123700
	Night	7% 9% 3 8% 5% 5% 5% 4 6% 8% 40%	123864
Transparency	Day	38% 6% 15% 26% 13% 2	123421
	Night	41% 6% 16% 24% 11% 2	123732
Seeing	Day	12% 9% 27% 30% 18% 4	16416
	Night	12% 8% 31% 35% 13% 1	25660

By Month

Percentage Cloud Cover SW (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	6% 14% 7% 14% 6% 6% 5% 3 4 7% 28%	3179
	11th to 20th	Day	6% 10% 5% 10% 5% 5% 9% 5% 6% 8% 30%	3180
	21st to end	Day	3 11% 5% 8% 5% 4 4 3 4 6% 47%	3820
February	1st to 10th	Day	8% 14% 5% 11% 8% 7% 5% 3 5% 6% 27%	1785
	11th to 20th	Day	7% 12% 5% 11% 6% 6% 6% 6% 7% 8% 25%	1755
	21st to end	Day	4 12% 5% 9% 8% 6% 7% 4 6% 7% 31%	1485
March	1st to 10th	Day	5% 9% 4 10% 6% 5% 5% 4 6% 7% 40%	4737
	11th to 20th	Day	6% 8% 4 9% 5% 5% 5% 4 6% 8% 40%	5000
	21st to end	Day	8% 16% 5% 11% 4 5% 5% 4 7% 9% 26%	5486
April	1st to 10th	Day	8% 10% 3 7% 6% 5% 5% 5% 7% 8% 35%	2422
	11th to 20th	Day	10% 12% 5% 9% 5% 5% 5% 4 5% 6% 34%	2567
	21st to end	Day	11% 9% 4 9% 6% 4 5% 4 5% 7% 36%	2600
May	1st to 10th	Day	13% 9% 3 6% 4 4 4 3 6% 6% 41%	6248
	11th to 20th	Day	12% 7% 3 9% 6% 6% 6% 5% 7% 9% 31%	6445
	21st to end	Day	11% 6% 2 7% 4 5% 5% 4 6% 7% 44%	7404
June	1st to 10th	Day	12% 6% 2 7% 4 5% 5% 5% 6% 9% 40%	3000
	11th to 20th	Day	16% 6% 3 6% 5% 4 6% 5% 7% 8% 34%	3000
	21st to end	Day	8% 4 2 5% 4 4 5% 5% 7% 8% 50%	3000
July	1st to 10th	Day	7% 3 2 6% 4 4 4 4 6% 8% 52%	4816
	11th to 20th	Day	5% 3 2 4 3 3 3 3 5% 7% 61%	4740
	21st to end	Day	3 2 1 3 2 2 3 3 4 6% 72%	5138
August	1st to 10th	Day	6% 4 2 5% 3 4 4 4 6% 8% 56%	4250
	11th to 20th	Day	5% 3 1 4 4 4 5% 4 6% 10% 55%	4028
	21st to end	Day	6% 2 1 3 3 3 3 3 5% 8% 63%	4521
September	1st to 10th	Day	10% 5% 2 5% 3 3 3 2 4 6% 56%	2331
	11th to 20th	Day	14% 5% 2 4 3 3 4 3 5% 8% 48%	2143
	21st to end	Day	8% 6% 2 5% 4 3 4 3 5% 7% 52%	2090
October	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 8% 9% 47%	3171
	11th to 20th	Day	4 4 1 5% 4 5% 5% 3 6% 7% 55%	3150
	21st to end	Day	8% 7% 3 6% 4 4 4 3 4 6% 50%	3062
November	1st to 10th	Day	13% 13% 4 9% 5% 5% 5% 4 5% 6% 31%	1568
	11th to 20th	Day	6% 10% 4 9% 5% 5% 6% 4 5% 8% 38%	1600
	21st to end	Day	7% 13% 3 10% 6% 5% 4 4 6% 8% 33%	1546
December	1st to 10th	Day	8% 16% 4 9% 5% 4 4 3 5% 7% 33%	2290
	11th to 20th	Day	7% 12% 4 13% 7% 6% 6% 5% 5% 6% 30%	2645
	21st to end	Day	3 9% 3 11% 6% 4 5% 3 5% 7% 42%	3498
January	1st to 10th	Night	5% 12% 6% 14% 6% 5% 5% 4 5% 8% 31%	6766
	11th to 20th	Night	6% 11% 5% 10% 5% 5% 6% 5% 7% 8% 32%	6780
	21st to end	Night	4 9% 5% 10% 5% 5% 5% 4 6% 7% 41%	7168
February	1st to 10th	Night	9% 12% 4 9% 7% 6% 6% 5% 6% 7% 31%	2614
	11th to 20th	Night	6% 12% 4 10% 6% 6% 6% 5% 7% 8% 29%	2532
	21st to end	Night	5% 11% 4 10% 7% 5% 6% 4 6% 8% 34%	2145
March	1st to 10th	Night	4 8% 5% 11% 6% 6% 5% 4 7% 8% 36%	5152
	11th to 20th	Night	7% 7% 3 6% 4 5% 5% 5% 7% 9% 41%	5000
	21st to end	Night	10% 16% 5% 11% 5% 6% 5% 4 7% 7% 23%	5489
April	1st to 10th	Night	8% 13% 3 9% 5% 5% 5% 4 6% 7% 34%	1974
	11th to 20th	Night	12% 9% 3 8% 5% 4 5% 4 6% 8% 35%	1781
	21st to end	Night	11% 8% 3 10% 4 5% 5% 4 5% 9% 37%	1800
May	1st to 10th	Night	17% 9% 2 5% 4 4 4 3 4 6% 43%	3732
	11th to 20th	Night	10% 7% 3 8% 6% 5% 6% 5% 8% 9% 32%	3446
	21st to end	Night	12% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	3470
June	1st to 10th	Night	14% 6% 2 7% 4 4 4 5% 5% 8% 41%	1400
	11th to 20th	Night	13% 5% 2 6% 5% 5% 6% 5% 7% 7% 40%	1400
	21st to end	Night	7% 3 1 5% 3 3 5% 5% 6% 9% 52%	1400
July	1st to 10th	Night	7% 2 1 5% 3 3 4 4 5% 8% 57%	2255
	11th to 20th	Night	4 2 1 4 3 3 4 4 6% 11% 58%	2220
	21st to end	Night	2 1 1 2 2 3 2 4 5% 8% 70%	2413
August	1st to 10th	Night	8% 4 1 5% 3 3 4 4 6% 9% 51%	2684
	11th to 20th	Night	5% 3 1 5% 4 4 5% 4 7% 11% 51%	2811
	21st to end	Night	10% 3 1 3 3 2 3 3 5% 8% 59%	3146
September	1st to 10th	Night	9% 4 1 5% 4 4 4 3 6% 7% 54%	1848
	11th to 20th	Night	13% 5% 2 5% 3 3 4 4 5% 7% 49%	2033
	21st to end	Night	8% 4 1 5% 4 4 4 3 7% 8% 53%	2090
October	1st to 10th	Night	9% 5% 2 5% 4 3 4 4 6% 8% 51%	3798
	11th to 20th	Night	6% 6% 2 5% 4 4 4 4 6% 9% 50%	3778
	21st to end	Night	7% 7% 3 7% 4 5% 4 3 5% 7% 47%	4465
November	1st to 10th	Night	11% 13% 3 8% 6% 4 4 3 5% 7% 36%	2730
	11th to 20th	Night	6% 11% 3 8% 6% 6% 4 4 6% 7% 39%	2800
	21st to end	Night	5% 13% 5% 9% 6% 5% 4 4 5% 8% 37%	2850
December	1st to 10th	Night	6% 14% 4 10% 6% 6% 6% 5% 5% 6% 31%	4890
	11th to 20th	Night	7% 11% 6% 12% 6% 5% 6% 4 6% 8% 28%	5546
	21st to end	Night	4 8% 4 9% 4 4 5% 4 7% 7% 45%	7458

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% 6% 16% 18% 3	3179
	11th to 20th	Day	51% 5% 15% 16% 12%	3180
	21st to end	Day	39% 6% 24% 26% 5%	3820
February	1st to 10th	Day	57% 6% 13% 16% 7%	1785
	11th to 20th	Day	52% 8% 14% 18% 7%	1764
	21st to end	Day	50% 6% 13% 21% 9% 1	1485
March	1st to 10th	Day	40% 7% 17% 25% 12%	4737
	11th to 20th	Day	40% 6% 17% 25% 11%	5000
	21st to end	Day	51% 9% 18% 16% 6%	5486
April	1st to 10th	Day	44% 7% 14% 25% 9%	2422
	11th to 20th	Day	50% 5% 11% 25% 8% 1	2570
	21st to end	Day	46% 5% 13% 26% 9% 1	2600
May	1st to 10th	Day	42% 5% 10% 23% 14% 5%	6248
	11th to 20th	Day	46% 8% 14% 24% 8% 1	6449
	21st to end	Day	36% 7% 14% 27% 15% 1	7406
June	1st to 10th	Day	39% 7% 17% 23% 12% 2	3000
	11th to 20th	Day	44% 7% 14% 22% 12% 1	3000
	21st to end	Day	30% 6% 17% 31% 13% 3	3000
July	1st to 10th	Day	28% 7% 16% 26% 19% 4	4742
	11th to 20th	Day	23% 5% 15% 33% 20% 4	4659
	21st to end	Day	14% 4 9% 30% 28% 15%	4976
August	1st to 10th	Day	26% 5% 11% 33% 21% 3	4233
	11th to 20th	Day	24% 6% 15% 40% 14% 2	4067
	21st to end	Day	21% 4 13% 39% 20% 2	4520
September	1st to 10th	Day	30% 4 13% 26% 19% 8%	2331
	11th to 20th	Day	35% 6% 14% 29% 14% 3	2143
	21st to end	Day	31% 6% 14% 31% 16% 3	2090
October	1st to 10th	Day	32% 5% 14% 32% 15% 2	3171
	11th to 20th	Day	29% 4 18% 34% 15% 1	3150
	21st to end	Day	36% 4 10% 38% 12%	3062
November	1st to 10th	Day	53% 7% 13% 18% 7% 1	1568
	11th to 20th	Day	43% 7% 19% 24% 7%	1600
	21st to end	Day	48% 6% 19% 20% 6% 1	1546
December	1st to 10th	Day	51% 6% 21% 18% 4 1	2290
	11th to 20th	Day	53% 8% 19% 17% 3	2644
	21st to end	Day	41% 5% 12% 27% 13% 2	3498
January	1st to 10th	Night	50% 8% 19% 19% 4 1	6766
	11th to 20th	Night	49% 6% 15% 14% 15% 1	6780
	21st to end	Night	41% 6% 21% 27% 5%	7168
February	1st to 10th	Night	51% 7% 13% 18% 10% 1	2614
	11th to 20th	Night	49% 7% 16% 17% 10% 1	2533
	21st to end	Night	47% 5% 15% 23% 9% 1	2145
March	1st to 10th	Night	42% 8% 18% 21% 11%	5152
	11th to 20th	Night	37% 6% 17% 32% 8%	5000
	21st to end	Night	56% 9% 16% 15% 4 1	5489
April	1st to 10th	Night	48% 4 13% 24% 10% 1	1974
	11th to 20th	Night	46% 6% 11% 22% 13% 2	1781
	21st to end	Night	45% 5% 14% 26% 10% 2	1800
May	1st to 10th	Night	43% 4 7% 27% 12% 5%	3730
	11th to 20th	Night	43% 8% 16% 22% 10%	3447
	21st to end	Night	39% 7% 15% 26% 13% 1	3470
June	1st to 10th	Night	41% 6% 16% 24% 11% 2	1400
	11th to 20th	Night	39% 9% 11% 25% 15% 2	1400
	21st to end	Night	26% 6% 15% 35% 16% 3	1400
July	1st to 10th	Night	25% 6% 16% 28% 22% 3	2220
	11th to 20th	Night	20% 6% 12% 36% 20% 6%	2178
	21st to end	Night	14% 4 9% 31% 30% 14%	2337
August	1st to 10th	Night	28% 6% 13% 29% 21% 3	2677
	11th to 20th	Night	26% 6% 15% 34% 15% 3	2838
	21st to end	Night	25% 4 13% 35% 21% 3	3146
September	1st to 10th	Night	28% 7% 11% 25% 20% 9%	1848
	11th to 20th	Night	34% 6% 13% 27% 15% 5%	2033
	21st to end	Night	29% 5% 14% 31% 18% 3	2090
October	1st to 10th	Night	31% 5% 11% 35% 17% 1	3798
	11th to 20th	Night	30% 4 15% 33% 17% 2	3778
	21st to end	Night	37% 5% 11% 36% 11%	4465
November	1st to 10th	Night	48% 7% 15% 21% 8% 1	2730
	11th to 20th	Night	44% 6% 19% 21% 10%	2800
	21st to end	Night	46% 6% 23% 18% 7% 1	2850
December	1st to 10th	Night	52% 7% 20% 15% 4	4890
	11th to 20th	Night	52% 7% 23% 14% 2	5547
	21st to end	Night	37% 5% 13% 27% 14% 4	7458

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	10% 6% 32% 32% 16% 5%	200
	11th to 20th	Day	11% 6% 37% 30% 15% 2	200
	21st to end	Day	11% 10% 36% 30% 11% 2	220
February	1st to 10th	Day	18% 13% 35% 25% 6% 2	293
	11th to 20th	Day	12% 6% 30% 34% 15% 2	300
	21st to end	Day	6% 9% 33% 35% 13% 2	249
March	1st to 10th	Day	11% 14% 30% 27% 14% 4	486
	11th to 20th	Day	9% 10% 34% 28% 13% 5%	500
	21st to end	Day	12% 12% 30% 28% 16% 3	550
April	1st to 10th	Day	12% 15% 32% 31% 8% 2	500
	11th to 20th	Day	12% 15% 33% 27% 12% 1	492
	21st to end	Day	16% 9% 26% 32% 14% 4	500
May	1st to 10th	Day	15% 8% 24% 28% 19% 6%	663
	11th to 20th	Day	14% 8% 24% 30% 20% 4	725
	21st to end	Day	17% 7% 20% 26% 22% 8%	789
June	1st to 10th	Day	15% 12% 24% 29% 17% 4	730
	11th to 20th	Day	17% 12% 28% 27% 14% 2	730
	21st to end	Day	10% 7% 25% 32% 19% 7%	730
July	1st to 10th	Day	6% 4 22% 36% 26% 6%	697
	11th to 20th	Day	8% 4 23% 38% 22% 4	668
	21st to end	Day	5% 6% 21% 33% 28% 7%	739
August	1st to 10th	Day	6% 4 20% 41% 22% 8%	545
	11th to 20th	Day	7% 3 19% 35% 28% 8%	477
	21st to end	Day	7% 8% 23% 29% 26% 7%	539
September	1st to 10th	Day	11% 8% 26% 28% 24% 4	490
	11th to 20th	Day	14% 6% 24% 31% 21% 3	490
	21st to end	Day	13% 10% 29% 32% 11% 5%	490
October	1st to 10th	Day	16% 6% 27% 28% 18% 5%	301
	11th to 20th	Day	10% 11% 30% 31% 15% 4	300
	21st to end	Day	17% 11% 34% 24% 13% 2	330
November	1st to 10th	Day	26% 9% 30% 24% 11%	300
	11th to 20th	Day	11% 16% 36% 30% 6% 1	300
	21st to end	Day	12% 10% 37% 25% 11% 5%	273
December	1st to 10th	Day	11% 11% 41% 27% 11% 1	200
	11th to 20th	Day	11% 13% 41% 28% 8% 1	200
	21st to end	Day	13% 8% 28% 33% 15% 4	220
January	1st to 10th	Night	12% 12% 35% 30% 11% 1	1000
	11th to 20th	Night	13% 10% 36% 31% 10% 1	1000
	21st to end	Night	11% 10% 37% 30% 11% 1	979
February	1st to 10th	Night	14% 9% 30% 32% 12% 3	800
	11th to 20th	Night	10% 10% 31% 38% 11% 1	784
	21st to end	Night	9% 6% 33% 34% 15% 2	660
March	1st to 10th	Night	9% 7% 34% 37% 12% 2	800
	11th to 20th	Night	11% 11% 33% 33% 12% 1	800
	21st to end	Night	12% 11% 29% 33% 14% 1	880
April	1st to 10th	Night	14% 9% 33% 31% 11% 1	634
	11th to 20th	Night	16% 5% 34% 34% 11%	593
	21st to end	Night	14% 10% 24% 40% 12% 1	600
May	1st to 10th	Night	15% 7% 23% 36% 18% 2	600
	11th to 20th	Night	12% 6% 26% 36% 19% 1	525
	21st to end	Night	18% 7% 23% 31% 18% 2	433
June	1st to 10th	Night	17% 9% 26% 35% 13% 2	400
	11th to 20th	Night	15% 8% 30% 35% 12% 1	400
	21st to end	Night	8% 6% 26% 42% 17% 2	400
July	1st to 10th	Night	8% 3 20% 48% 21%	380
	11th to 20th	Night	7% 4 26% 45% 18% 1	368
	21st to end	Night	4 4 23% 45% 23% 2	416
August	1st to 10th	Night	8% 3 22% 41% 25% 1	529
	11th to 20th	Night	7% 2 21% 42% 27% 1	564
	21st to end	Night	10% 4 24% 38% 24% 1	627
September	1st to 10th	Night	11% 4 25% 43% 15% 1	570
	11th to 20th	Night	15% 5% 22% 41% 17%	703
	21st to end	Night	10% 6% 30% 38% 14% 2	760
October	1st to 10th	Night	15% 8% 27% 34% 17% 1	760
	11th to 20th	Night	14% 8% 31% 33% 12% 2	760
	21st to end	Night	13% 10% 36% 32% 9%	860
November	1st to 10th	Night	17% 11% 35% 30% 7% 1	975
	11th to 20th	Night	14% 13% 39% 28% 6% 1	1000
	21st to end	Night	11% 10% 38% 33% 8% 1	1000
December	1st to 10th	Night	12% 8% 35% 32% 11% 2	1000
	11th to 20th	Night	11% 10% 39% 29% 11% 1	1000
	21st to end	Night	13% 9% 35% 33% 9% 2	1100

Page generated at 2025-07-02 23:30:12. Version ac07

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